Some time ago i red about a way to modify the straight pipe with an adjustable baffle

, so You can get some backpressure. It was designet mostly for HD riders, but I think ??? it might help somebody here too.
The deal is this:
You get a washer with a diameter slightly smaller than the ID of the pipe. Weld a 6mm bolt to it and You have something like a sunflower. You drill a 6mm hole in the uderside of the pipe about 1" from the end. Slide the "sunflower" in the pipe and drive the bolt thru the hole. Put a lock washer and a nut and tighten it good. Put the proper wrench in Your pocket and go for a ride. See how the bike runs all thru the range. Turning the "sunflower toward "fully open" or "fully closed" find the "sweet spot"

.