ok heres how it is. i can start the car but the idle drops down then goes back up then repeats.(motor shakes alota). when i drive it, the car cant rev any higher then 4000rpm. i change mostly all the vacuum lines. im thinking its my fuel pump or fuel filter.

89 GTU

 

check the plugs, wires, coil packs, vacume leaks, possibly do a timing check to, also a compresstion test to be sure.