Turbo kits are geared toward the people who want cheaper power. The unfortunate consequence is that the power is... cheaper. Cheaper fuel management, cheaper parts, and cheaper performance standards. This kind of cookie-cutter respone is not meant for the decidedly non-cookie-cutter engine that you posess. You sound more inteligent than average, please do the research into a custom setup for your engine.
You should really be able to answer your own question. If you want to keep your block virgin, you will need to run lower boost on a very steeply trimmed compressor. Your ITR head will flow a lot more than the others around you, so you need a turbo that you can't catapult past efficency with.
If you want to take the "R" out of your ITR and drop the compression, sleeve it, and put forged steel everywhere, then you can run rediculous double-digit boost.
Tuning is a must, either way. Get somebody good, not joe schmo frat-boy-with-a-rom-burner.
Sleeving your block would be an insurance policy, and you can replace your internals with forged high-compression slugs. The lighter weight means somthing, but that is all excessive if your goal is less than 400whp. It dosen't mean it's bad. Hell, I did it.
If your goal is in the area of 400whp, then you should probably look at some other aspects of your turbo setup, such as a rigid crossmember, thick axles, and a traction bar setup.
Edit: My spelling is terrible, but not nearly as terrible as b's drunk spelling...
