How To Build a Custom Subaru WRX STI

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If you’re looking for a car that’s going to turn heads coming out of the shop—something stylish, but performance-oriented that’s going to take to modifications like nobody’s business—then the WRX STI is likely already close on your radar. Aside from its baseline brilliance out of the box, the
Subaru WRX STI
can be customized beyond your wildest dreams!
But with all the choices out there, it can be easy to be left with a bit of choice paralysis between factory customizations and aftermarket mods. Luckily, we've scoured the online world for all the tips you need to mod the perfect custom Subaru WRX STI.
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2021 Subaru WRX STI customization options

While Subaru has yet to release a 2022 WRX STI, the 2021 Subaru WRX STI is a fantastic compact sedan designed for drivers who like to drive for fun every once in a while. It’s a consistent winner on the rally track because it’s highly responsive. On top of all this, it’s a legendary base for custom jobs galore!
The 2021 Subaru WRX STI has a starting MSRP of $38,170. Also available is the
STI Limited
trim, which adds a rear spoiler or wing, leather seats, blind-spot monitoring, lane change assist, rear cross-traffic alert, and a moonroof to the WRX STI’s already upgraded 310 horsepower engine, high-tuned suspension, 19-inch alloy wheels, upgraded brakes, and steering responsive LED headlights. This added bit of luxury will cost you about $4,500 more.
There are no available engine upgrades, but there is a strong community of aftermarket support for WRX STIs, and they’re incredibly easy to modify. You might even want to try modifying one yourself! Still, these flat-4 turbocharged AWD engines are great out of the box, and they’re available only with six-speed manual transmission.
In terms of factory upgrades, the standout feature of the STI limited is still the option for a large rear wing or a trunk-mounted lip spoiler for added aerodynamics.

The best Subaru WRX STI mods

Subaru offers an impressive selection of customization options for the WRX STI, but you can also make it your own with custom mods. Here are a few types of upgrades to keep in mind when building a custom WRX STI. 

Air/oil separator

Any engine is going to get some oil in its engine vents, but the WRX STI’s turbocharged engine is likely to be especially bad in this regard. Essentially, your oil level is going to decrease faster than it would with a more common engine, and excessive oil gunk in your intake system can cause some problems that range from annoying to dangerous if left unchecked.
An aftermarket air/oil separator (AOS) can stop this from happening by rerouting excess oil that would otherwise end up in your ventilation either into a catch-can to go back into your engine or an automatic draining system that would do this for you on a continuous basis. This upgrade will reduce your oil consumption, increase the octane of your fuel by avoiding oil dilution, and improve your engine’s performance.


Tires are one of the simplest aftermarket upgrades you can do for a car, and great tires can make a massive difference in your driving experience. They’re a huge matter of safety and performance, so it’s never a bad idea to shell out for the best option on tires. You’re going to improve performance and fuel efficiency and ultimately save money on gas if you’re using fresh tires with good treadwear ratings.

Cold air intake

If you want your turbocharged STI’s engine to really scream, you can add a cold air intake. An aftermarket cold air intake that’s larger and is able to pump more air into your engine will free your engine’s turbo for higher combustion by bypassing the limiting design of the OEM intake. You’ll get more power and better performance from your engine. This is a super easy mod to do yourself!


If you’ve already upgraded your tires, the suspension is another great place to look, despite the fact that your WRX STI’s engine will already have a highly-tuned suspension. Coilovers allow you to fine-tune your suspension to your liking and allow you to upgrade to high-performance tires without overpowering your stock suspension.

How to find affordable car insurance for your Subaru WRX STI

All this dreaming about one of the coolest custom rally cars on the modern market can be really tiring, so now that we’ve talked about some great upgrades for your WRX STI, sit back, relax, and let
find you the best
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coverage you can get!
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By Cameron Thiessen
Updated on Feb 01, 2023
Reviewed by Jessica Barrett, Senior Editor.
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