On a bike with the catalytic converter still in the header pipes (meaning still on the bike) there is just not that much difference in back pressure with a slip on pipe vs stock.
I wouldn't think so either.
Another interesting note- headers, pipes, mufflers, etc are tuned/sized for specific back pressure and flow to work together to produce desirable performance, efficiency, pollution control, and noise control. Altering it in unusual/mismatched ways that do not work together can sometimes actually lead to lowering overall performance or just shifting compromises around.
A real "performance" exhaust is one that is designed (and tested) specifically for the size/type/behavior engine (and its implementation) and includes all the matched components from the exhaust ports on the engine all the way out the tailpipe. This is what I was taught by a race mechanic.
Seems like most people just slap on an aftermarket muffler and perhaps a short section of mid pipe and pretend all the extra/different noise is actually doing much more than extra/different noise.
Or I might just have no idea what I am talking about, that is always a possibility too. I will ask my friend some specific questions about the "missing" at lower RPM. as described, this weekend.
