When I decelerate I'm getting back firing. What could be causing this. Thinking intake problem maybe.

 

Tighten your exhaust to make sure there is not an air leak.

 

if you're using slip ons, be sure to use some high temp rtv at the joint before sliding on the mufflers. i prefer the black permatex high temp rtv silicon sealant. be sure also to wipe the joint afterwards while the rtv is still wet, or you'll have a mess. it's likely at that joint if you're using slip on mufflers.

 

Could be caused by a lean condition.