some problems and questions

I would guess that the straight pipe might would be better, but leaner, since there's no back pressure.
The best would be an expansion pipe, it bounces the unburnt gases in the exhaust back into the cylinder, kind of supercharging the engine, but from the exhaust, not the intake.

sickbikeparts.com sells these, and I think spookytooth does. Do a search on them.

It will probably have more imaginary power due to being loud. It may have a little more top end if you get the jetting right.

Hi xzackx. Hoping to see some photos of your different problems so that we can evaluate it with full detail.