I am also having the same type of problem for my 90' deville 4.5. I replaced the cap, rotor, fuel filter, wires, and plugs. The car runs fine when I am in 2nd or 3rd gear but when I get to a stop sign the car idles roughly and sometimes cuts off. My mechanic suggested replacing the distributor but after this yune-up he said it should be okay. Could this be the my distributor or could it be something else.