Grit Valve
2000 4.6 Vouge
The manual does not say there is an IAT sensor in the MAF, it says that the temperature is derived from the MAF as I recall.
I'm not aware that BBS software is derived from Testbook, the Nanocom is basically the Faultmate software which is I believe unique to BBS, it does not run in the same hardware or software environment as Testbook.
Maybe you have a fault as well so the iat is part of the maf and by the -38 that tells me there is a fault I still say it should rise you can always do a live feed on fuell plugged in and unplugged should give you an indication that fuell is being upped with sensor plugged in and reduce with it out.