Working on a VRT with a 3" HPX Blow through maf currently battling the following codes

16486- Mass Air Flow Sensor (G70)
P0102 - 35-00 - Signal to Low

17550- Load Calculation Cross Check
P1142 35-00 Lower Limit Exceeded

I used the calibration sheet from HPX replaced the sensor checked wiring .

You can let the car idle all day no codes once you rev it and or drive throws those codes.

I m guessing it has to do with the lower voltage calibration

HPX vs Stock





 

Is this the old Motronic VR6? When they introduced the later HFM 5 series with the glass housing and ceramic substrate this helped massively with the reverse flow problems which is why many 12V owners sometimes have problems with turbulent flow whereas the newer ones don't. There is also a difference on the low flow math between variances for example the V6 4motions use the 62mm ID whereas the R32's use 71mm so the math is different there - has that been calculated correctly?

http://www.maf2maf.com/wp-content/uploads/2014/05/Bosch-HFM5-Sensors.pdf

I would look at these low ranges - I've not really done much on these older Motronic VR6's but I believe it's a 256x1 map v's 512x1 for the 5 series.

Few figures to look for in the hex if you are doing it on the newer HFM5 style;

http://nefariousmotorsports.com/forum/index.php?topic=10321.0

take a look at this bin it might help you. two different cars I know but the voltages are probably the same ?