Zd30 maf sensor location

[the evil twin]

I just looked up some thread s and again one by ynot and he says maf sensor gets contaminared by engine breather emissions and i assumed this meant breather is upstream . This isnt the only post that says that , so i guess its a common misconception.

Tony is correct, the MAF Sensor is "upstream" from the breather and it does get coated by emissions,

In a turbo charged engine such as the ZD30 there is a condition called turbo surge.
Turbo surge is much less problematic in a VNT or VGT such as the ZD30 than that of a conventional Turbo but it does still occur.
The surge exists when a rapid unloading of the engine and thus the turbo means the high pressure induction air in the intercooler plenums (approx 32PSIA) can momentarily surge back thru the turbo inlet and air induction pipes towards atmosphere and therefore contra to the normal flow.

This momentary contra flow means that over time the MAF will get a slight coating of engine breather residue which also encourages any fine particulates post air filter to also adhere to the sensor.

If you pull out a ZD30 air filter after a few thousand K's and have a look you will see an almost circular patch of black oily residue on the filter where it faces the induction plumbing.
This residue deposit is also due to the turbo surge and gives you an idea of what is also coating the MAF sensor.