Sometimes ill be driving and my idle for some reason will drop VERY low (500RPM) and the car will sound and shift like crap. ie, put clutch in and revs drop like a rock and there is a severe bog. Also ill put the clutch in after cruising at say 3k RPM and the revs wont stop at 1k like usual, the engine just pluments straight to 0 and shuts off as if i had the key outta the ignition. Itll be driving normal and then just start doing this, then after awhile itll go back to being fine. Just got new spark plugs, have a VAFC , AEM and exhaust. Any ideas to fix it or things to check for?

 

vafc is the culprit. check all connections again.

if not, sounds like you might have a bad throwout bearing or the pressure plate went dead.