I just put on the WB slip on E series... and the instructions say if you get some backfiring at deceleration that it's running a bit lean- and to remove some of the rings. I'm currently running 12 rings that originally came with the WB pipe. How much backfiring is normal? It only popped a few times and didn't do it on every deceleration. I'm also running at about 4800 feet above sea level (Utah). Everything on the engine is stock.. I put a K&N air filteron as well?

Any insight would be helpful!