I have a 98 SH. The motor has 117,000 on it still running strong. For some reason when the engine is idling and i rev it alittle after the revs come back down they sometimes drop very low almost causing the car to stall. This only happens every once in awhile. The car is mostly stock just headers, intake and exhaust. Any ideas on what could be causing this ?

 

Might wanna do a valve lash adjustment