The GE uses a competely different type of AFM, different means of measuring air and completely different means of comunicating with the ECU.
Up until Bob and the good Doctor helped me figure out several things (they deserve all the credit there) and Bob wrote a few code updates you would have been told the MAFT Pro would work as of v4.65, but it didn't.

(v4.80 works great though)
EDIT:
NOTE: I am in NO WAY directly referring to HPF or any other vendor in the following. This is merely intended as an explanation as to why YOU as the buyer MUST do your own research and double check the info before buying something as vehicle specific as an ECU piggyback.
***** When dealing with any shop the people you're talking to are *usually* salesmen, first and foremost. Sure they may work on cars, they may work on MKIIIs, but it doesn't mean they know everything about them... especially the often dogged N/A. You shouldn't EVER expect a vendor to know all the answers, it's great when they do, but don't count on it. There are any number of reasons you may get the wrong information, they may be too busy to get all the info, you might say something which leads them to believe you are using a different setup than you are. They may even tell you the complete and factual answer, but YOU might mistaken it to mean something. Don't blame the vendor, just make sure you've got ALL of the facts straight before you buy.