Correct me if I'm wrong here. You have an auomatic transmission and 65 moh translates into about 3100 rpm?
Is it possible to slide the transmission selector into "2" and cause the same problem at a lower speed but at 3100 rpm.
Or even in low"1" see if you can cause it to sputter.
If it does then the problem is engine speed related and not necessarily horsepower related.
Check it out it is an easy test.
I want to determine if it is fuel supply related or ignition control related. High RPM with light pedal uses les fuel. I'm thinking spark advance exhaust recirc.....
fuel pressure.