I took my 15g (long story) out of my 91 744 so I could change all the seals in the oil filter bracket (I am hunting down oil leaks). Is it me or the engine temperature was kinda hot? Would it be the mixture was lean? If so, I got no error codes. I will put my A/F gauge back and may see about yanking one of the spark plugs out and ask it what it is seeing. Otherwise, what could be making my poor turbine wheel white? If this is important, this exhaust manifold and turbine housing are *not* ported.