Anyone tuning a Harley for peak power will most always use a 2 into 1 type exhaust system.
On my last '08 110" bike, I had true duals and they told me it would rob power, which I was almost sure I could feel.
Sometimes something that sounds so very cool, is NOT he best for you.
I remember many years ago friends of my dad had Harley Sportsters and it was Halloween. They pulled their standard short pipes off and made up very long pipes that went low to the rear wheel and then swept upward about 3' each. These pipes basically robbed them all their performance.
I couldn't help but wonder the first time I saw a M3W how they ran as good as they did with that very long exhaust system. But if the cam is "adjusted" to run with the length of pipe and backpressure, I could see them working okay.
I know a tuner that does baffles for Harleys and also does his own dyno work. He's found that with his tune the larger baffles make higher peak power, but a mild loss in mid range. The smaller baffles, read quieter, made more average hp and lots more mid to low range torque.
I believe what most of you guys want is lower mid range torque and max peak at WOT.
