2009 Mini Cooper s N14,79k ml. had a problem with cold rough start and lost of power. Several codes with multiple cylinder misfire and p115d. Replaced HPFP and fuel filter. Cold start issue is gone,then new air filter and MAF sensor installed,inspected intake hoses for leak. still having same issue.Yesterday had P2187 and P3091 and I did clear this codes. today after start iI drove about 10 miles in the highway and came out again P115d. Can carbon build up make that problem? Please,help

 

Cheapest check will be looking for boost leak first. Check all your intake tubes and those worm-gear clamps. Make sure there are no leakages or air leaks. If this doesn't show any signs, then could be your turbo needing a look at. Good luck.

On suspicion of carbon build-up problem, just remove the intake manifold and have a look, it's an easy job and worth a try.