Pequod

Hi all, My 2008 S5 coupe with the 4.2 V8 and around 62k miles started shaking slightly during a drive and when I got home it started shaking a lot more while idling and displaying a flashing engine warning light followed by a solid ECU light. Diagnostics show a P0300 code for random/multiple cylinder misfire and a code for cylinder 3 misfire, along with a P130A "hide cylinder" code. A few months ago cylinder 2 was misfiring with the same symptoms and I had swapped the coil pack from cylinder 2 to 3 to isolate the issue, but mysteriously the misfires stopped altogether. For some more history, this car had all fuel injectors replaced a few months ago and has some old fault codes which have been present since I first got the car a year ago, P1068 "intake air switch over valve open circuit" and P1571 "left engine mount solenoid valve short to plus". As for now, replacing the coil on cylinder 3 made no difference, same for the spark plug. I got a camera in and the injector isn't leaking and the piston head itself looks fine. I am about to use a continuity checker to check the plug which goes into the coil pack and make sure that connection is fine, but beyond that I've no idea what to check. I would appreciate any suggestions for a potential cause of this issue and what to do next.