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Discussion Starter · #1 ·
Currently have a 2021 STI with the following mods:

Cobb SF Intake w/ airbox
Cobb EBCS
Cobb LF BPV
Cobb Catted Downpipe
Cobb AP w/ Pro-Tune
Invidia R400 exhaust (catted)
IAG AOS

Does anyone recommend upgrading the fuel system with the above listed setup? I saw a Cobb Fuel System upgrade kit for about $1700 on the Cobb website but not sure if it’s overkill. Moreover, I was told I wouldn’t really benefit from a cylinder 4 cooling mod. I don’t plan on going above stage 2 plus for at least a couple years. Thanks in advance for the recommendations/ thoughts.
 

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2020 Subaru WRX STI
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You should probably get a fat turbo. Replace injectors with rubber hoses so the fuel just dumps straight in.

Nobody knows what you want to do with your car. If you have a purpose then its much easier to modify your car. I prefer to modify a lot of suspension and handling parts, then power, then looks (in that order).
 

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Not much more you can power wise that will be very noticeable except go flexfuel which I ran in my previous STi for almost 10 years since before any “kits” Add injectors, fuel pump, e85 should give you another 50whp/50 whp over a 93 protune. Super fun car for street, daily duty.
 

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Discussion Starter · #6 ·
You all are 100% right, I forgot to mention my goal. I would like a build that resembles the performance and quality of the S209 STI. My budget is about $15k. This is my first Subaru as prior I used to drive German cars like the BMW 435i. I’m unfamiliar with the platform and where to invest my money in to get a solid street car. I don’t drive aggressively and am meticulous with service intervals/ regular maintenance. This would also be my daily driver.
 

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You all are 100% right, I forgot to mention my goal. I would like a build that resembles the performance and quality of the S209 STI. My budget is about $15k. This is my first Subaru as prior I used to drive German cars like the BMW 435i. I’m unfamiliar with the platform and where to invest my money in to get a solid street car. I don’t drive aggressively and am meticulous with service intervals/ regular maintenance. This would also be my daily driver.
in terms of the power, i'd add an equal length header to that (killerb setup). add the killer b oil pickup/baffle combo, the cyl4 cooling mod, a quality aos (iag or killer b), and a flex fuel setup (which would be injectors/pump/fpr/flex sensor/tune), and then run e85.
spend the rest of your budget on quality wheels/tires and suspension mods (not necessarily ALL of the budget, just what you need).


oh and also you might need a clutch for the wtq you'll get going e85, although i wouldnt personally do that till it's necessary.
 

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SWP 2012 GR Hatch
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I'd add an inlet for the added throttle response (and flow).
The stock one is a miserable piece of hardware.

While you could argue for or against injectors, a fuel pump is still a good idea.
Obviously do injectors if you have any intention of going flex-fuel.

Fuel pressure reg helps smooth things out a bit too with fuel delivery.
Idk if the 2021's still get stumble, but it made a massive difference on my 12' in smoothing out the low speed on/off throttle.
It's not jittery anymore.

Headers.
Equal length headers.
Idk if you're a fanboy of the Subaru burble, but I put Tomei ELH on my car this year.
The difference was massive.
Way more low end torque, and power in general.
It even made a difference on a regular Cobb Stage 2 tune before I went in for my pro tune.
After the pro tune it was just scary.
ELH is like if you could go one downpipe-level upgrade above the downpipe itself.
Killer B makes a sweet piece of kit, but if it's not in the budget, Tomei makes a good option too.
Tomei uses a lesser version of stainless, so I got mine Cerakoted for 150$.
Headers is an absolute recommendation, I'd do headers before an exhaust or intake even (I already did).
Also, ELH balances out the exhaust port temps because you don't have one runner getting hotter exhaust gasses, so it does a bit of what the cyl 4 cooling mod aims to do as a bonus.
Headers.
 
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Since it’s a newer one, I’d replace the boat anchor 19” stock wheels. A lot of people go down to an 18”, either 8.5 or 9.5 width, depending on what you’re doing with the car. Hoping to do this next year… every year when I switch to my winter set (which is by no means light weight) it’s amazing how much more responsive the car feels, and I regret not having things together enough to have taken care of this by now for the summer setup.
 
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