what slip on has most hp. increase? HMF Bills or t-4?
I don't care about sound. This is for slip-ons.
power i am looking for is mid-top end.
also, looks, and fit are considered. thanks

 

It depends on what other mods you have done to your bike. A pipe really isnt going to do much without a jet kit or filter. As we see more and more here to quote someone "More ain in, More air out". Do a search.