Stumped as well... My only input is sounds like some electrical gremlins put there by PCM... Not too familiar with anything newer than my boat from a fuel delivery stand point, are you carbed or some form of TBI or fuel injection? I know mine will sometimes stumble coming off idle if the engine is heat soaked after sitting. I can get up to about 2200-2500RPM and the engine will start to struggle. This doesn't happen when the engine is cold or I am just starting out and is a recent development for me.
'86 Comp TS6M - Reborn 2016
Riding a HO Sports CX Ski