When my S4 gets up to operating temp.. it sounds like im making popcorn in my exhaust! The poping is random but quite frequent. It pops like this at idle as well as any other constant RPM range. My first thought was to pull the cam covers and make sure it didnt skip a tooth. After inspection, things look ok. Temp sensors are within spec. What other sensors should i be looking at that affect timing? So before I assume the worst and have the valves re-seated, my question is.. has anyone had this happen to them and found a solution?!