What's the propane for? On EFILive there's an IAT correction factor you log/apply before monkeying with the VE/MAF to aid with this phenomenon. I need to do it to my GenIII stuff as well. I'm guessing you rescaled your MAF then?
Tailgating.
Supplemental fuel and octane. Adds about 6 octane points.
There are a few tricks I needed to do to tune this on the Gen 4 2.5 Bar OS using a MAF and propane. First problem was the 60pph injector ceiling (before scaling the tune) which creates calculated torque load issue that puts the truck into limp mode when it is exceeded The work around is to tune the MAF to have a hole to account for the supplemental fuel injection. It is a 20% undercut. It is a workaround for a hard-coded issue you cannot address with HPT, but can with EFI Live.
Very annoying.