I'm trying to increase my knowledge on cars (especially BMWs) and learn how to diagnose and fix problems.

my cylinder 2 has a misfire (N62B44) it usually happens when the engine is cold and then goes away when the engine warms up and clear the code

I already swapped the ignition coils and the spark plugs and so far cylinder 2 is still misfiring

Can someone give me a list of things to diagnose or check? we think it could be the ECU because we replaced it a while ago which was not needed because it had a previous timing issue, the people who changed the ECU didn't seem so good at what they were doing and we think the ECU is bad.

I have an advanced Foxwell scanner that can go into details and read everything but the problem is my dumbass OBD2 port also does not work which we also think is from the ECU. so I'm kind of stuck in a bull shit situation

the car also has a previous idle misfire without any code or SES popping up, but this one is different because you can literally feel it when you accelerate and SES turns on after giving some gas

by the way, I drive the car pretty hard (I have a heavy foot)