[CapriRacer]

I wonder if the RF brake caliper is hanging up - causing a drag on the entire car. The problem here is getting it to duplicate itself.

Since you can drive the car, do so until it acts up again. Then tap the brake several times while driving to see if the symptoms go away. If they do, report that to the brake shop.

If the symptoms do not go away, I'm voting for an ECM going bad. But that ought to leave code in the OBD system. So I'm betting on the brakes