I had a bad catalytic converter and I replaced exhaust (no emissions rule in my state so shop replaced exhaust system without catalytic converter). After repair, car was still running and idling rough so I changed spark plugs...this helped but did not completely resolve the issue. The car still runs rough and has a rich smell to exhaust and sometimes gets RPMs high between 10 and 30 mph. Car is throwing a P0300 code, which is multiple random misfires, I have not changed coils yet. I am hoping to get input from someone else's experience.

 

I'm not familiar with your car, but does it have regular spark plug wires or is it coin on wire? If regular wires, I'd try inspecting them for green corrosion first. If you see any, replace them. If not, take a look at the coils, for sure.