The IS300 community’s never-ending pursuit of naturally aspirated power has made one thing clear — catback exhausts and intakes will only get you so far. Headers are where it’s at if you want to free up a few more ponies and actually feel the difference.
This of course depends on whether or not you’ve installed an air-fuel controller, how aggressive your tune is, and what supporting upgrades you have installed.
Only trouble is that finding a good set of headers for the Gen 1 XE10 IS300 at the time of writing is quite difficult.
The best IS300 headers have been discontinued and finding them used is damn near impossible. Especially long-tube race headers like what Xerd and Mazzuri used to make.
But that doesn’t mean you have to be stuck with your stock manifold. In this article, we’ve listed some of the best headers and OEM exhaust manifold replacements that you can buy for your IS300.
Supporting Upgrades
When browsing for IS300 headers, you’ll come across some that have integrated catalytic converters and others that don’t.
If you wish to comply with emissions norms and don’t mind a slightly restrictive header design, then the cat-con-equipped options are worth looking into. From a performance standpoint, you want to get catless headers.
The Gen 1 IS300 has 3 catalytic converters and 4 O2 sensors; 3 on the exhaust manifold and 1 on the y-pipe. So by installing aftermarket headers, you’ll be removing the two cats that are located before one of the O2 sensors.
This will give you a check engine light, but it can be avoided by using an O2 simulator as it will ensure the ECU doesn’t throw error codes. We also recommended that you install an air-fuel controller, and it’s always a good idea to get a tune.
IS300 Headers: Your Best Options
Remember, if you don’t find exactly what you’re looking for, custom headers are also an option, especially if you intend on keeping your 2JZ-GE naturally aspirated.
With that out of the way, let’s get into the list you’re here for. Below we’ve listed both catted OEM-replacement headers, and catless race headers. Choose the latter if you want performance, and the former if you want a solution.
Flowmaster
Manufacturer: Flowmaster
Part number: FLO-2054276
Construction: Stainless steel
Primary tubes: 2.5”
Design: Short tube, integrated catalytic converter
If CARB compliance is not at the top of your priority list, then the Flowmaster headers are worth looking into. Note that they are Federal/EPA approved.
Even though they’re listed as “catalytic converters”, the package will include the replacement manifold with integrated catalytic converters.
The cat-cons that you get with these aren’t made by Flowmaster themselves, but they’re of adequate quality. Installation is straightforward, with the exception of having to remove the throttle body to fit them properly.
Packaging and finish can be a hit or miss, but rest assured that they’ll work just fine when you bolt them on properly. They come with 3 O2 sensor ports and are a direct fit for 01-05 IS300s.
MagnaFlow
Manufacturer: MagnaFlow
Part number: FBHB452843
Construction: Stainless steel
Primary tubes: 2.5”
Design: Short tube, integrated catalytic converter
Buy on: Amazon
The MagnaFlow header is an ideal replacement for your OEM exhaust manifold. It is mandrel-bent, CARB compliant, won’t give you a check engine light, and your IS300’s exhaust note will get only slightly louder and deeper.
It’s not easy to find aftermarket headers that come with genuinely good quality catalytic converters. Because of how expensive the catalysts are, manufacturers tend to cut corners to keep costs down.
MagnaFlow headers are an exception as they are known to contain more precious metals in the cat-con than what you get with most other options. The quality isn’t OEM-level, but it’s as good as it gets.
Quality control issues are common with these headers, but the 8-year / 80k mile warranty offsets that risk.
Dorman
Manufacturer: Dorman
Part number: 674-642
Construction: Stainless steel
Primary tubes: 2.5”
Design: Short tube, integrated catalytic converter
Buy on: Amazon
If you’re on the lookout for a simple OEM replacement exhaust manifold and don’t want to spend a lot of money, the Dorman headers are your best option.
These are available in both CARB compliant and non-CARB compliant variants. The latter is much cheaper. A minor niggle that you’ll run into is that your OEM heat shield might not fit these headers.
OBX
Manufacturer: OBX
Part number: 10-1901-3S
Construction: Stainless steel
Primary tubes: 1.6”
Design: Long tube, catless
OBX makes both long and short runner headers. What we’ve listed here is the catless long runner variant designed for IS300 owners who favor performance.
Surprisingly, these headers don’t get too loud and have an acceptable amount of drone which is very unlike long runner headers.
Expect a noticeable mid-range bump, depending on the tune of course. Overall, these headers are a fantastic deal. They’re inexpensive, well constructed, and not very difficult to source.
The only complaint with these headers has to do with the low-quality gaskets that come with them. You can remedy that by purchasing OEM gaskets.
Figs/PPE
Manufacturer: PPE Engineering
Part number: IS300_ELHEADER
Construction: Stainless steel
Primary tubes: 2.25”
Design: Stepped primary long tube, catless
This is as close as it gets to the likes of Mazzuri and Xerd headers. Jointly developed by PPE Engineering and Figs Engineering, these are currently among the best IS300 headers you can buy.
The equal-length stepped primary tubes have excellent exhaust scavenging characteristics and allow for multiple peaks in power.
As a result, you can expect a consistent step-up in power from as early as 3500 rpm. Even more so with the right supporting mods. It’s worth mentioning that there’s a wait time of several weeks if you order these, but it’s well worth it.
Concluding Thoughts
Replacing your OEM exhaust manifold with aftermarket headers is a bit of an undertaking, but if you don’t do it yourself, expect to pay around $350 to have a shop do it for you.
We recommend keeping the stock y-pipe unless you have a complete exhaust system build in mind. Keeping the last stock catalytic converter is also a good idea as it will keep the black soot off your bumpers and also help to keep the exhaust volume low.
If you’re wanting to go one step further, consider a catback or axle-back exhaust system for your Lexus IS300 wagon or sedan.
Do you know of any obscure, high-quality IS300 headers that can still be purchased today? Let us know by leaving a comment below.