Having owned an 05sti(4 years) and an 08sti (2 1/2) I can tell you with full confidence that the STI is a great package for tuners but NOT faster than an e9x m3. Hell a more real comparison would be a 335i(s) even then the 335i will destroy it.
The STIs and a lot of other AWD turbo cars are great to get to 70-80, but after that it's a face plant. Not to mention the STI engines when pushed will fail, lots of problems with turbo creep.
Coming from the subaru world I can tell you that you'll get a few glory runs followed by weeks and months of dyno time, adjusting front mount intercoolers, finding the right turbo, tuner, etc. It's just not worth it. AP is a great OTS package, but it's just walking you into injectors and a pro-tune which will walk you into a different turbo maybe meth in, then moving your top-mount intercooler to front mount..then all of a sudden you realized you just spent 12k on top of a 35k car and realibilty is out the door.
Last edited by Nine; 05-13-2011 at 10:15 AM.