Recurring super knock/misfire/limp mode under boost on N55 — third time, now cylinder 2 (previously cylinder 5). Plugs/coils recently replaced. Insights?

Hi everyone, This has happened to me three times now on my N55 (assuming 335i/X5/etc., ~165k miles, stock tune, good 91/93 fuel). 

•  First time (~10k miles ago): Pushing past 3,500 RPM, car stuttered badly and went into limp mode. Tech thought bad plugs — replaced them, issue gone. 

•  Second time (~2k miles / couple weeks ago, during a 3,600-mile road trip): Same symptoms under higher RPM/boost. Tech found some plugs broken/foreshortened and coils burnt. We suspected the first tech used cheap/fake Bosch (Mexico-made). Replaced all plugs and coils with genuine — fixed. 

•  Third time (today): Normal highway driving, suddenly stuttered into limp mode. Pulled over, cleared codes, drove home fine in Eco/low RPM. No issues at light throttle. Symptoms are identical each time: •  Fine at low RPM/Eco mode cruising. 

•  Stutter + limp mode only when pushing/boosting (3,500+ RPM). •  Clearing codes temporarily fixes it until next hard drive. Last time affected cylinder 5; this time cylinder 2. Haven’t pulled plugs/coils yet to check for damage, but only 2 weeks/~2k miles on new ones. 

I have another car, so no rush to drive this one. Before taking it to a tech, any ideas on root cause? Fuel injector leak/failure on the affected cylinder? HPFP starting to go? Something else? 


Codes I’ve seen before: things like 152D08/152508 (super knock + injection cut-off), 140010/140510 (misfires), 140001/140501 (injection switched off) — but cleared now. Really appreciate any insights from N55 owners who’ve chased similar recurring issues!

F15 X5 Limp mode (N55)