[2001 330i e46] P1343 engine light?

[Stupidrobots]

So I picked up a 2001 330i with a ton of miles because it was in great physical shape and ran like a top, the previous owner was a BMW mechanic and the engine had basically a new top end. It ran great for a few weeks then i got some shuddering in the engine and a CEL. I read the code and it says P1343 Cylinder 1 Misfire with Fuel Cutoff. To me, that means a bad ignition coil and the internet seemed to confirm that. Ignition coils aren't expensive and they're luckily easy to replace on this sauerkraut rocket so I did it, reset the code, and the engine went back to running buttery smooth as it should....for a day. Then it came back and I'm a bit mystified. What else should I check here?

[randy72877]

Vacuum leaks can cause misfire codes. A smoke machine is best for finding them. Intake boots break a lot too, particularly the small branch that connects to the idle control. Ccv system is also a common problem. It could also be a bad spark plug or injector. You can switch them to different cylinders and see if the misfire moves. Compression test to rule out mechanical engine problem. Good luck

Sent from my SAMSUNG-SM-G870A using Tapatalk

[Stupidrobots]

So I've done ignition coil, vacuum lines, and fuel injector. I still get an intermittent limp-along mode and check engine light. I think I've taken it as far as I can go. Going to have a mechanic take a look at it and do some proper tests.