I'm just getting my project running and I have a stand alone temp sensor just in front of the TB. Now in my previous set up there was no MAF. My intake temps were, at idle/start up just above ambient (80F*) and normally didn't get too much higher except for heat soak. But after installing the 1g ECU with 2G MAF, My intake temps were showing near 120 just after start (haven't driven the car yet) and I started to wonder if the temp sensor was bad, but after shutting the car off, the temp would start dropping immediately.

Is it the MAF that's heating the air that much?

Isn't this just the measuring spot difference?
Don't you have an intercooler? If so, pre intercooler v.s. post intercooler.

Is this still the old Porsche you swapped the DSM ECU into?
Are we talking about the exact same sensor in the same location by the TB?
How were you measuring the temp both times?

There isn't anything in the 2G MAF that normally would heat up. The airflow measurement is done by ultrasonic counting of the vortices generated in the airflow not by measuring the cooling effect on a heated wire like a GM MAF. The two other sensors in the MAF are IAT and absolute barometric pressure and neither should be heating the air.