[fleetfoot]

Preface: I've had the vibration issue during overboost since I got the car at 6500 miles. I took it to the dealer and they detected the vibration, but said it was normal for a stiff M car. During the same visit, CBS called for new spark plugs, which the dealer installed under warranty.

So after the dealer visit I was driving my M2 hard in the mountains last weekend, and the vibration at WOT in third gear turned into something worse: a CEL. I had downshifted into third, went WOT with overboost and immediately the engine backfired, went into limp mode, and threw a CEL with 3 codes for: random misfire, misfire on 3, and misfire on 4. I pulled over, restarted, and they cleared. But then I had the same thing happen about 30 minutes later with a misfire only on cylinder 3, so my mountain drive was over.

I took it to the dealer and after a bunch of diagnostics (including a smoke test) they determined the coil on 3 was bad. They went ahead and replaced the coil and plug on on 3. The CEL is gone and I haven't felt any vibration during overboost since.

So I think my vibration was likely caused by a failing coil.