[sperry]

First, in the grand scheme of things, a bone stock '06 WRX is a ridiculously fast car. Seriously. It's got about twice as much power as it needs to get the driver into trouble. I wouldn't do anything to it until you've had some instruction and practice taking it to the limit. Hit up some autocross and PDX days before you do anything mod wise.

Second, like Dean said, the #1 thing that will make the car faster is the driver. There's a reason a 90hp Miata can smoke a 600hp Viper at the track, and it's all in the skill of the driver.

Third, after the driver, the wheels and tires are by far the best bang for your buck in performance. Remember, everything else you do to the car (engine, brakes, suspension, driver, etc) has to work through the tires. So, get some nice lightweight 17x8 wheels and some good Max Performance summer tires. That $1000 and change will be by far the best $1000 you'll ever spend on going faster. For example, when I changed from street tires to race tires at the track my lap times went down by more than the $20,000 worth of engine, suspension and brake mods I had done previously. (And Dean was still just about as fast as me on his street tires... there's that #1 mod being the driver thing again.)

Fourth, the next best mod is suspension. Swaybars and endlinks are a great starting point. Some struts and lowering springs are the next step up and will get you about 90% as much handling as full coilovers for much cheaper and are much more streetable. Finally, some full on coilovers are nice for their adjustablility if you're looking for that last bit of speed.

Fifth comes the brakes. Good pads and fluid are really all a WRX needs. Some SS brake lines don't hurt, but don't really make you stop better, they just make the pedal feel better. If you're hitting the track all the time, a full on BBK is much nicer than having to rebuild your brakes and bearings once a year, but most people don't track that often for it to be worth it.

Sixth, finally you're ready for more power. The Cobb AP and a turbo-back exhaust is hard to beat for power vs. price. A 2.5L WRX with just that is going to be in STi-land powerwise, and it's going to be relatively reliable, especially if you get it dyno tuned specifically for the car (the off the shelf maps are passable at best). Once you go bigger than that, then you're it's big $$ time. If you go for a turbo, for example, you're also going intake, intercooler, injectors, fuel pump, tuning, etc. And above that comes built motors.

What doesn't work: BOV... there's no point... unless you like ricer noises attracting attention. Some (like me) will argue they hurt performance. Cat-back exhaust... without a tune, they sound cool, but really offer no performance. CAI, without a tune, they're bad for the car... with a tune they gain nothing until you're way up in new turbo land. Turbo-back exhaust w/o a tune can also be bad for the car, as it can lead to boost creep and overboosting. Manual Boost Controllers are maybe the worst thing you can put on the car w/o tuning for them, and in most cases, the a proper tune on the stock Electronic Boost Controller works better.

But above all, remember that a bone stock WRX, especially the 2.5L, comes with *plenty* of power... more power in fact than the stock tires, suspension, and brakes can really handle. Learn how to drive the car (and you'll learn the fastest on the stock bits) first, then start with the handling and braking before upping the power.

At least that's my 2 cents after doing this for 8 years and like $100,000 in mods.