Turbo's are designed as a system. Just tossing a bunch of leftovers together might not be the best method to build one. The quality systems also include a timing retard module. Tube length from the turbo to the carb is important too, shorter means less turbo lag. There is also a lot of technology incorporated into the design of the impeller, vanes, and an oiling system. Done wrong, it's a really easy way to gernade an engine.