D&D insisted the mid pipe with slip on system they sold me needs no rejetting, as long as no other modifications have been made..., i.e. air box mods, filter changes etc.
I guess its a case by case basis, but my bike runs perfect! No flat spots just haulin a**!
Just a hint of rumble on decel, nothing that would bother anyone, not popping, just purring, nice, very nice.
Ill have to run some miles before pulling a plug to show you (my bike is just a weekend playtoy and Ive got some out of town stuff coming up, wont be riding much), I would guess its lean as ever (stock) but I dont expect its dangerously lean, its running too good.
PS check the scorpion website, they said they are trying to make all pipes dyno perfect with no rejetting.