[mwebb]

Originally Posted by primemover

Anyone have any ideas? My understanding is that most cars shouldn't go open loop until much higher load.

TPS relative to rpm , look at knock retard as well, it may be going to open loop because
the system detects excessive ping followed by knock retard

not the air / fuel map.

swap OEM size wheels and tires back on and re test
or
try a tank of High test to see if knock retard is lessened OR you can get a higher load value prior to changing to open loop
BEFORE chasing ghosts

ultimately
increased drag coupled with change in final drive ratio
changes everything