Kerker 4-1 Gains the most HP and sounds unbelievably good. Not cheap but worth it. But no matter what you buy DON'T get cobras and I'd stay far away from ANYTHING from Planetmax I don't care how nice their stuff is Jon will Dick you around for sure. Ask anyone here.
I disagree w/the comment about Jon Cornell of Planet VMax. I know people have had issues w/him, and from reading those issues, I understand why they would be unhappy.
I have had a different experience prior to buying a 4/1 of his manufacture, I emailed him and received prompt, detailed, responses which answered all my questions. On the basis of my research from him and other sources, including the forum, I bought it. The workmanship is great and while I haven't yet installed it, I know from hearing the clips and seeing others' comments, I will like the results. I actually like the quiet nature and appearance of the stock system. Stealth in noise is a good thing! And, yes, I know Planet VMax systems are NOT about "stealth in noise!"
I do think the Kerker 4/1 sounds best, I have one of those too, not installed, as I do not want to cut my centerstand flange brackets.
Matter of fact, I have a backlog of things to do to my bike, but haven't been able to make the time to complete. I have acquired a lot of parts, but no time to get things done. Maybe when I put the bike up for the winter...:rofl_200::rofl_200: