My turbo takes a while to spool? How can I get it faster?

Okay, I just bought an audi tt- 2000.(manual of course) It's upgraded to the 225 hp turbo. Full exhaust, 15lbs of boost, intake...etc alot of other small mods. If i start in 2nd gear, and am at 4000rpms, and floor it, it moves veryyy quick, once i hit redline, i shift and then it goes down to about 4500 and it gets slow. It seems very slow. What can I do to change that. I believe it's the turbo.