Im by no means an expert, but the following may help a fellow newbie like me by accident.
On a recent V8 we were having trouble with, it was running like a 3 legged pig, then ran great, would idle then wouldn t, ran great at 5000 revs then didnt, I pulled into my garage and popped the hood at that moment the garage light blew and I was standing in a pitch black garage.
Holy shit, it was like Australia day in the engine bay, with sparks streaking from almost every plug lead where it entered the coil, and at the plug end where it was arcing out on the manifold.
There is no better way of seeing whether you have stray arcing from plugs, leads or the coils that in the pitch black.
Might help someone out.