I am new around here.
I thought I should add to this as it helped greatly, too bad I found it a little late, let me explain.
Bought a 2015 F30 335i in August 2021.
I had a slight misfire/hestiation on idle, which kept getting worse. I didn't scan it as it wasn't severe and I planned to get fresh plugs with the oil change anyway.
I swapped in fresh NGKs (silzkbr8d8s). When I removed the OE plugs, I noticed that cyl3s plug was darker, even around the threads. Some research indicated a possible injector leak, i figured that was probably the reason for the "slight" misfire/ hesitation on idle.
Started the car with the fresh NGKs. I had a terrible (car shakes, Drivetrain malfunction message, etc) misfire. Scanned with ISTA+ and cyl 3 was the culprit. Swapped coils around, still cyl3.
So I went to the next step and worked on getting a new Bosch injector from Goldwagen and ordered the necessary tools. Installed it and I still had a misfire on 3.
At this point I was also stumped. I came across this thread so I decided to swap out the plug from cyl3 with cyl4 and the misfire moved to 4.
Never in my mind would I have imagined that a new plug could be faulty, I guess we learn everyday. I got a replacement from Midas and the car is in great shape.
Thanks for the thread guys, it helped.