I own way more silencers than I can pubically admit to. The last count was 10. Its almost became a hobby in itself....I bought most of them on the auction site. FMF, Bill's , Pro Circuit, SPES, Noleen, Various stock models, and an answer carbon fibre model.
I dont notice much of a difference in any of them. Some sound different. Some might rev slightly faster, but none of them add much, if any horsepower. I like the performance of my fmf silencer , but it is poorly constructed. It fits, but just barely.
The pro circuit silencer is good. It fits perfectly. It revs slightly slower than the fmf model. It is also longer.
My favorite is a Noleen brand I found on egay. Still, if I said it added 5% , I would be imagining things.
If the silencer your loking at is similar in length to your stocker, dont expect much.