Maggie 2300, Cam, not tuned by me. Brand new trans, trying to solve this.
at part throttle, around 30-50% the car will shift to third, then slip (sounds like a wanna be downshift for a bit) before finally going back tin 3rd and continuing. It seems to shift fine at WOT, and at VERY light throttle.
see attachments. Note frame 5100 on.