Why the crossover exhaust pipe on '09 Street Bob?

The question is, why is there a crossover exhaust pipe?
1. Does it improve the performace?
2. Does it improve the emissions?
3. Does it reduce the decibels?
4. Other?
I don't think that Harley Davidson designed it that way for looks.
My '03 Road King has a stock crossover exhaust pipe. The configuration is different to match the design of the touring bike with one muffler on each side.

My mechanic said it makes the engine run better, but he didn't exactly explain what "better" meant. When I updated the Road King with Rinehart slip ons (plus some other stuff), I asked the mechanic about true duals instead. He said it might not run as well with true duals. It runs fine with the stock crossover pipe. Dyno'd at 79 hp.
Last edited by SailorDon; Nov 1, 2009 at 09:26 AM.




