I have a '96 Seville STS and it's all of a sudden giving a P0300 misfire code. It feels like it's running on 7 cylinders. I've changed plugs and wires. I found 1 wire cut slightly but I still have the same problem. Still runs awful and giving the P0300 code. It seems like the car was missing when the engine was cold but as soon as you drove for 1/4 mile, it ran fine. If it's one of the 4 coils, how can I check them to see which one and if it even IS a coil. I've heard it could also be a vacuum leak or compression since the P0300 is a "Random Misfire" instead of cylinder specific. How possible could that be?