I installed a set of GrimmSpeed P&P exhaust manifolds along with a BPM Crossover about 2 weeks ago. So far I have noticed a big improvement in throttle response and the acceleration feels so much smoother when the boost comes on. Here are a few pics. The quality of some of the pics aren't so great but they give you an idea.
P&P vs Stock Manifolds:
Justin is a great vendor. He was very helpful and quick to answer any and all questions that I had. I also got some other stuff from him and got everything in very short order with no problems. If I was to do it over again I would get them coated too: