car stalling!!! help plz

ok heres my problem…when ive been driving my car for like an hour after completely warmed up and everything…i will stop in like a parking lot or red light and the cars RPM’s drop below 500 and then go back up and do this a few times and the car shakes bad…then sometimes putting the car into drive from park the RPM’s drop below 500 again and sometimes will stall…i cant seem to figure the problem out…i have new spark plugs and wires new dizzy cap and rotor, new fuel filter, changed oil and filter,etc…all routine maintenece stuff…here are some things i think it is…vacumm leaks, timing belt loose or timing is off, fuel injectors, fuel pump, compression leak maybe…if u guys can help me out id appreciate it…thanx in advance


well without more information i would have the fuel pressure checked next, and the ignition timing.

are you getting a check engine light? error codes?
what year is your car?

my car doesnt get ne check engine lights…my car is a 1990 GS