Originally Posted by JetFalcon
So is it possible for any kind of Subaru out there to outperform a BMW M3? Mainly in terms of acceleration and handling turns
It's certainly possible, maybe not practical. But if I were to take the cheapest, most painless route possible to beating a late model M3 in most performance measures, it would look something like this...
As far as pure acceleration:
Buy a used, 2.5L STi that's bone stock (don't want to inherit anyone's headaches).
Buy a catless downpipe ($290), used catback exhaust ($400) bigger fuel pump ($85) and injectors ($500).
Get it protuned to run on e85 (~$400).
One the power is taken care of, buy some quality tires ($800), lower it ($275), get some performance brake pads and fluid (~$150) and it should be close enough to an M3's performance level to make it a driver's race. It's also the cheapest route to having a truly high performance car out of a Subaru.
If you really want it to be no question, do thicker sway bars, strut tower brace, bushings and before the protune also get a Process West TMIC and a bolt on turbo (there are several) or a FMIC and rotated setup. At this power level a better clutch would be necessary too, and while you're there also do a lightweight flywheel, and transmission and engine mounts. Take out the back seat, spare tire, put as little gas in as possible and go on a diet.
This is obviously a much more expensive route, and you're severely affecting the ride comfort, noise, vibration and drivability of the car. At this power level, forged pistons would be smart too. Costs rise exponentially, and practicality drops through the floor as you try to make a cheap car comparable to an expensive one. It sure is fun though!