sometimes when i start my car up, the rpms will go from 1500, then bog down really quick to the point the engine almost dies, then jumps back up to 1500rpm.... and does that for a few seconds, then smooths out to a regular idle.

also, when im driving down the road and i let off the gas i can hear the engine reving down and then back up again... but it doesnt do this all the time it randomly does it while i drive, even sometimes when i go to give it gas itll bog down really bad, ill let off the gas pedal and then hit the gas again and it goes fine



could it be the coil maybe? its a MSD coil wired up with what im guessing is the original ignition system minus the distributor. when i first got my car the check engine light was on because of a bad knock sensor, and for another code which i dont remember, i was told it was because of the way the coil was wired up

 

oh yeah, and sometimes when i put the engine under load it feels like a carburator bogging down, and a second later it picks up and takes off

 

i'd check your timing or vaccum leak

 

how would the timing cause the rpms to go all over the place when the throttle is at a constant position?