It's very possible, and has been done. You will need up and down pipes, an intercooler, blow off valve, tubing, gauges, voltage clamp, knock sensor, fuel pump, and a rising rate fuel pressure regulator. I think that's everything. The biggest problem with the WRX TD04 turbo on the EJ25 is that the TD04 can't push enough air to maintain boost at higher revs. The TD04 will be moving about 575 CFM of air at redline, while the engine is going to be moving ~625 CFM. That TD04 is pretty close to maxed out on the 2.0L, and adding that extra .5L is just too much for that turbo. But it will work, give about 5-6 PSI max, and will spool quickly (max boost at around 2500 RPM), but the boost will taper off to about 2-3 PSI by redline. But if you want to go with the TD04, check out http://www.uniquemotorsports.com/ , Chad has a list of all the stuff needed, and even sells some of the important parts, like the up and down pipes. I have a set of them, and they are really well built. I was going to do this to my car, but then decided I wanted to at least wait until the warrenty was up, so I've got a bunch of stuff just sitting around. But I've done a bit of reading up and researching on this subject, so ask any other questions you might have; I might even know the answers!