Engine is misfiring?

Hi ive been having this misfire on my cavalier for a long time. Its always had a very very slight rough idle for years but just until a month ago it finally got worse. Long story short I would drive it and when I would come to a stop it would occasionally start misfiring but wen I drive it drives perfectly normal. Only wen stopped or idling especially it would misfire intermittently. One night I got stranded cuz I was driving and the engine light started flashing I lost power so I pulled over, I checked the plugs and cylinder 4 plug was carbon fouled it was black and dry. I cleaned it and got it home and the code was a p0300 random misfire. The plug boots are still semi new so I changed the plugs, coil pack, and ignition control module that sits on the coil pack. After that and the car was fine. Just a few days ago the car started acting up but differently this time. Whenever the car idles it misfires a little but sometimes a lot and its at random. Also when I put it in reverse the car starts misfiring like crazy. I checked the plugs and there are normal. The new coil fixed the fouling problem but ONLY when idling and in reverse the car misfires. No more codes came back ever since I cleared it a month ago. I put fuel injector cleaner in it, measured resistance and listened to the injectors, sprayed the engine for shorts but the problem still exists. Im just stumped on how this car is acting especially with the car misfiring like hell in reverse