As for warranty...with a turbo I'd say it's a lot trickier than your normal "bolt-on" performance parts. The rules state that the mod, regardless of what it is, has to be proved to be a result of whatever problem you have. Unfortunately when you are doing a turbo, you are definitely gonna be throwing down a lot more power so a lot more things can go wrong. Your engine itself, your clutch, your tranny....a lot more things can be blamed on the turbo if things do go badly. I'd say that if you aren't fully prepared to deal with the fact you aren't gonna be covered under warranty, then don't do it.
A lower pressure turbo has been proven to be fairly safe....provided it is setup right. When it comes to turbos, if you try to cheap out on everything...the results will show I think.
