Lexus IS300 Performance Mods

Lexus IS300 Performance Upgrade Guide

Jake Mayock

Meet Jake

Jake is a founder of 8020 Media and TuningPro. He has over a decade of experience in the automotive industry including parts sales, writing, DIY modifications & repairs, and more. Jake is currently converting his N54 to a single turbo and building a Miata track car. He’s an experienced, hands-on automotive enthusiast who delivers in-depth, well-researched content.

First gen models utilized the 2JZ-GE engine, the non-turbo version of the legendary 2JZ-GTE, which is a 3.0L straight-six producing 217hp and 218lb-ft. of torque. Third-gen models added forced induction via a smaller 2.0L turbocharged inline-4 producing 241hp and 258lb-ft. of torque.

Since one engine is naturally aspirated and the other is turbocharged, the mods we discuss differ. This guide will focus on the 2000-2005 naturally aspirated 3.0L IS300. These engines can produce about 225whp with tuning, an intake, headers, y-pipe, exhaust, and adjustable exhaust cam gear. We’re going to discuss each of these mods in-depth below and also cover engine power limits for those looking to push things further.

Lexus IS300 Performance Mods - Best IS300 2JZ Upgrades

Engine Power Limits

The mods on this list will get you somewhere around 225whp. Without breaking out a ton of money or adding forced induction, this is about the max you can expect. The world record NA 2JZ-GE has 320whp but the owner apparently has about $20k-$25k into the build which is just not worth it, in our opinion.

Now, what about with a turbo? On the stock block with stock internals the 2JZ-GE can handle about 400whp before investments in internals and block strengthening is needed. While it can make it to the 400whp mark, it is generally agreed that ~350whp is the safe limit without significantly impacting reliability. Even 500whp+ is easily achievable, but it will require some expensive upgrades.

Lexus IS300 2JZ-GE Mods

  • Intake
  • Headers
  • Y-Pipe
  • Cat-back exhaust
  • Adjustable exhaust cam gear
  • ECU tune

1. Cold Air Intake

An upgraded intake is one of the easiest first mods to make to virtually any car. While adding an intake to an otherwise stock IS300 won’t provide a ton of performance benefits, it will once the other mods mentioned are added. Creating more power requires more combustion, and air or oxygen is a fundamental component of combustion.

On a stock 2JZ-GE an intake will probably get you about 2-3whp. However, when combined with these other IS300 bolt-on mods it will provide 7-10whp of gains. So while it might not be the most impactful first mod, it is an essential one and also one of the most cost effective ones for starters.

There are various different intake options for the IS300 3.0L. They are all virtually the same and offer the same benefits.


  • 7-10whp and wtq when fully modded
  • Increased air flow
  • Cool intake sounds

2. Headers

Headers are one of the most important standalone mods for the 2JZ-GE. More power means more exhaust gases. The stock headers become highly restrictive once more power is added which creates a buildup of backpressure within the engine. The backpressure causes exhaust gases to seep back into the combustion chamber which results in lower amounts of oxygen in the combustion chamber and therefore less power. Headers will also help decrease exhaust gas temps and engine temps making them a great mod for reliability as well.

Outside of making your engine run healthier, headers are good for about 10whp and 10wtq power gains due to the reduced backpressure.


  • About 10whp and 10wtq power gains
  • Slightly louder exhaust note
  • Reduced exhaust backpressure
  • Improved exhaust flow

Catalytic Converters

Both the headers and the Y-pipe house catalytic converters in the IS300. The biggest power gains come from deleting both of these cats because they are predominantly what causes the restriction. The caveat here is that deleting catalytic converters is against emissions regulations. The alternative option is to get high-flow cats but these are more expensive and options are limited due to the age of these 2JZ-GE engines now. The power difference is probably about 3whp less for high flow catted options.

3. Y-Pipe Upgrades

The Y-pipe bolts directly up to the headers, connecting the headers to the cat-back portion of the exhaust. 2JZ-GE headers combine into two pipes, each one housing three cylinders of exhaust gases. The y-pipe is called a y-pipe because it connects to the two header flanges and then combines into one single pipe where it then bolts to the cat-back exhaust.

The Y-Pipe is the second most restrictive portion of the exhaust since it houses a catalytic converter and sits behind the headers. Therefore upgrading the y-pipe can help further reduce backpressure within the exhaust system and increase power. Since the restriction from the y-pipe is a bit further away from the engine it provides slightly less power gains than the headers. However, it still provides a solid ~8whp when going with a catless option.


  • About 8whp and similar torque gains
  • Slightly louder exhaust note
  • Better exhaust flow and reduced backpressure

4. Cat-Back Exhaust Upgrade

To be honest, a catback exhaust system is probably the least worthwhile mod on our list, unless you want the louder exhaust sounds. Catbacks are the most expensive exhaust component and provide the least power gains. With that being said they do reduce some exhaust backpressure and are good for about 2-3whp.

Just like with headers, there are $150 exhaust systems and $500 ones. They are really all the same, but picking your exhaust brand is a bit more important than headers. Headers won’t add too much additional sound to the exhaust whereas a catback will. So picking a cat-back exhaust for the IS300 really comes down to sound preference and looks.

I tend to tell people to save the money and spend it elsewhere from a performance perspective. If you want the sound, go for it. Otherwise the money is better spent on suspension or handling mods unless you are inching for every last bit of power the 2JZ-GE has in it.

Exhaust Benefits

  • 2-3whp and torque
  • Louder exhaust note (maybe good maybe bad)
  • Reduced backpressure (minimal)

5. Adjustable Exhaust Cam Gear

The most unique and probably advanced mod on our list is an upgraded exhaust cam gear. Exhaust valve timing on the 2JZ-GE is controlled by an exhaust gam gear. The adjustable cam gears were primarily made for people running aftermarket cams with higher lift, but they can also benefit IS300’s with the stock camshaft with bolt-on mods. The gear allows you to adjust valve overlap; more valve overlap is beneficial for NA cars.

Whether an exhaust cam gear gains power or not is a debated topic. However, what is known is that it does improve the power curve and delivers more consistent power and acceleration. Dyno charts show gains around the 6-8whp mark but most owners notice the improvements in the power curve over the power gains. Folks with turbocharger setups have shown gains near 20whp with an adjustable exhaust cam gear.

For a modded IS300 with stock cams most people recommend setting the exhaust cam gear to -4 for optimal performance and gains.


  • 0-8whp gains and similar torque gains
  • Improved power curve
  • Better acceleration
  • More consistent power, carries to redline
  • Better throttle response

6. ECU Tuning

Last on our list, but the most important mod to bring everything together is a tune. Tunes adjust the ECU and variables such as fueling, timing, etc. to improve power and performance. Tunes are especially important once mods are added as the stock ECU tune isn’t optimized for more air flow, less backpressure, and so on.

Unfortunately, flash tuning the stock ECU isn’t an option for these cars. The Apexi SAFC 2 was the old tuner of choice but it is no longer produced as far as I’m aware. The options today are getting a standalone ECU, albeit they are quite expensive and rather advanced from a user friendliness perspective. We recommend working with a tuner and digging into more research and specifics on the options available. We’ll dig into this topic in its own post down the road.

A standalone ECU is also required for adding a turbocharger so it’s a good investment whether you plan to add FI or stick NA. The options on the market are Haltech, MaxECU, AEM, Link, ECU Masters, etc.

Standalone ECU Benefits

  • Approx. 10whp and torque gains
  • Improved gains from all other mods mentioned
  • Better engine reliability
  • Improved power curve and overall performance

Forced Induction Considerations

The mods we list on here will get you to about 220-230whp for manuals and around 210whp for eshifts. You can break past those numbers and stay naturally aspirated but it’s very expensive. It will require a stroker kit, meth injection, an aggressive tune, and maybe even some nitrous. The stroker kits are about $7.5k, so let’s just ignore this as an option for now.

So, if you want more than 230whp the best option is to add a turbocharger. Read our guide on IS300 turbo upgrades before proceeding with the mods we discuss on this list. Your whole exhaust system will change when a turbo is added and your car will need to be re-tuned so adding things like headers and y-pipes is a waste of money since they will eventually be irrelevant.

Also, keep in mind adding a turbo kit will end up running you close to $5k on the low end for a budget setup and up to $10k+ for a proper setup once you add the boost controllers, timers, widebands, fuel management systems, upgraded injectors, full exhaust systems, etc.


If you want to spend a few thousand bucks to get a 225whp IS300, go for it. However, the best way to add power to the 2JZ-GE is to add forced induction via a turbo kit. These engines can handle more than twice the power they produce from the factory, but the only way to get to those levels of power gains is through turbocharging. These engines simply do not mod well when left NA, albeit an extra ~40whp over stock isn’t terrible.

Overall, the IS300 has a lot of tuning potential. The caveat is that the tuning potential all lies in turbocharging and a proper turbo setup is going to run you $8k-$10k.

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One Comment

  1. I have 03 5 speed with intake some eBay headers and stock y pipe and straight rear cat 3” tip honestly I’m looking in get exhaust gear and get it tun I mean with I/H/E I beat a 2.0t Audi to cars on my car only one person in audi

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