The carbon pro exhaust is quite expesive, but they always make a decent product.
I talked to Sparks on the phone, they claim to make 3-4hp on the bottom, 4-5 mid, 3-4hp on top. They always have a great pipe, not the quietest but definately very solid performers. I would bet that these number are very accurate, and are not exagerated!
I talked to ESR on the phone. He is claiming 8hp more on the top. They have a quiet style endcap available also. The pipe sells for 585 plus 65 for a quiet syle end cap!
I talked to LRD, and they told me that the full exhaust will be done today, he did not have any numbers to give me, but would call me back with them. But I know they make a decent 4 stroke exhaust so we'll see what they come up with.
I talked to Duncan, and he claims to have the best 450r pipe available. But he did not give me any numbers to back it up. He did tell me the gains are 15-20%.
Lets not forget HMF, they are making 7 bottom, 7 mid, 4 on top, and it makes 13+lbs of torque. They are also the least expensive of all the pipes, and have a quiet core available for $35
The real question is how honest are these guys with their dynos?