If you're going to stay with the stock manifolds and plumbing for now, they do have nice replacement turbos, as RS Speed mentioned. I used a different set up, due to having custom made intake and exhaust manifolds. I have the GT2876r's with internal gates, and 0.64 turbines, using twin 3" dumps into a single 4" exhaust. That is a little much if you want instant response, but I don't mind... They come on a tad bit later than stock, but pull like a freight train all the way till I want to let off.
My turbo's link
Edited turbine housing ar