Tyty, I was going to say that pcc was onto something there with the throttle kick adjustment comment. The way you are describing the late shifting and letting off the throttle, that would be my first guess, but you are telling us you already adjusted it. Hmm... What else would cause this? It's a mechanically driven transmission, not electronic.

Is that cable taught? Or is there a little slack? You may want to adjust it some more and make sure there is a little slack. You will know quickly if that was the issue or not. The tighter it is, the higher the shift points are.