I think the problem lies in the ecu. The wiring is right.
I think the problem all boils down to the airflow. The stock maf reads .8 to 1 volt at idle, even with the engine chugging along at 400rpm it doesn't go below .8 volts.
With the hpx maf in the stock 3.5 inch piping at 800 rpms it reads .550 volts at the ecu then bounces to .080 (effectively off as far as the ecu is concerned) then back to .550 volts. I have tested directly out of the maf with a vdc probe and see .420-.450 volts when this happens.
Also when it does this it will trip a maf code in the ecu. However if i raise the idle to 1300 rpms it will read higher voltage function correctly and not trip a code in the ecu.
Ive gone back and forth from stock to the hpx, and the stock functions correctly, the hpx functions as well, i just don't think the stock ecu has the ability to resolve voltages below .550 volts even though there are tables for it in the ecu.
In the mean time it seems I'm stuck.
Either i go to a z32 maf and hope i don't max that.
or put the hpx maf in a 3 inch tube instead of the stock 3.5
Im sure the fact that this is in a blow through application doesn't help.
not sure what ECU/car you are using this for, but some ECU's (eg. Z32) indeed have 0.5V as the minimum voltage hardcoded in the code that processes/translates the AFM voltage.
anything lower then 0.5V when the engine is running and the ECU assumes the AFM is defective and starts running in safemode.