THe hardest thing I have found is figuring out specs on second hand turbos and judging how to size them for my application.
For instance, say i wanted to go the twin turbo route, would two smaller turbos off of some import/small car work well? And what about having one turbo that spools up fast for low end grunt, and the other that spins up and compresses better through the upper rpm band?
So many little questions.
Also, do most donor turbos come equipped with a wastegate or is this something I'd have to add on myself? How are they controlled? computer, or mechanism?