The car: 2006 9-3 aero V6 turbo - manual transmission - 110k miles
When turbo boost pressure gets close to the red under acceleration - either with high rpm: 3rd gear/50mph and max throttle OR low rpm: 6th gear / 45mph and max throttle - engine cuts out abruptly, and ‘stutters’ until you ease off the gas. Sometimes this triggers ‘limp home’ mode, where it will not apply any boost pressure again until car is restarted. Sometimes check engine light is sometimes triggered, with one of either: cylinder 5 misfire, or overboost (turbo pressure) codes.
Trusted mechanic has replaced ignition coil (twice to be sure), swapped spark plugs with cylinder 4 (still sees issue in cyl 5) and now thinks it is either a bad fuel injector (from what I hear these are very reliable) or a major ‘valve’ issue which would entail a presumably very expensive head rebuild.
Is there anything else that could cause this? Before we eliminate the injector and Im presuming looking at a head rebuild. is there anything else to check / pray for? If it does turn out to be some valve issue, could the car be driven for a very long time as is, or would it deteriorate further?