Originally Posted by dazedone
Also check your pcv valve and system, up to 30% of engine intake air can passthrough the pcv system. If its clogged/restricted you will run rich.
Why? The PCV system pulls air from the turbo inlet (downstream of the MAF sensor), and vents that air into the intake manifold (downstream of the MAF sensor). If it's clogged, you'd just have more air going through the regular intake tract (turbo, IC, etc) and less air going through the motor, but either way the amount of air entering the cylinders should be the same as the amount of air that went past the MAF sensor.