i am riding with my hmf slip on on the back.. and i dont hear any backfiring. I just put it on and started riding.. so far like i said no backfiring. I seem to have a lot more power in the lower gears also.. so i guess its working right... is there any signs of running lean i should look for? what are they?
Everyone said to rejet, and i never did, and my pipe sounds fine and performs well... in a few weeks its getting jetted.. so i guess the way it is now i can ride it.

 

THE PLUG WILL BE A GLOSSY WHITE INSTEAD OF A DULL OR POWDER WHITE.

 

Heres a realy good article on jetting and symptoms of rich and lean. I think this is what youre looking for.
jetting