[icingdeath88]

Swap what WRX stuff exactly?

For 350 to the wheels you'd need:

A trans that can handle it - PPG geared 5-speed, 6-speed, or some sort of built auto. I kinda doubt a stock WRX trans would last long with much abuse.

Some kind of engine management that can deal with bigger injectors, at least the 370cc SR20DET ones. 6 of those will max out around 350-370, more with increased fuel pressure. The ECUtune stage 2 setup (370s and a Z32 MAF) is the obvious choice, but still lacks tuning for the specific car, and is therefore imperfect. 550cc injectors would be better and safer and give more headroom.

Built shortblock - 6 STi EJ257 rods should be able to handle 350 hp at least. Eagle H-beam rods can be special ordered in a set of 6 if you want something extra strong. You'd want to have some lower compression pistons made.

A turbo, or supercharger. A high compression ratio engine with big cams and a proper exhaust and intake would get you to around 300 probably. Bigger power means boost.

The engine itself is quite strong, but will have cooling issues if run at high RPMs for a long time (or something, there's an enormous thread about it around here somewhere).

An 02 wrx would have the 2.0t engine, and no engine internals (AFAIK) would swap. The 5-speed would. The turbo is too small to move enough air for a 3.3L engine. You'd need two of them, and even then there are good enough single turbos that a twin-turbo setup would be very hard to justify. Swapping the engine itself would be possible, but no one's done it and it would be kind of stupid to swap a ~200 hp engine for another ~200 hp engine. An STi engine would start to make sense, but even then... eh.

Start by clicking the "Turbo project" link in my thread and have a look at how much the pistons cost. Then if you haven't been completely knocked on your ass, do some research here on the forums, there have been several big-ish power builds in the last ~5 years or so. What you want can be done, but it demands serious amounts of research, time, effort, and cash.