I had to do this on mine to make it act right.  I dunno why it wouldn't adjust correctly, but it wouldn't.  so I added layers of split tubing to the sensor knob, until it bottomed out when flooring the pedal.  
This is 3 or 4 layers of slpit hose used as a spacer.  Back then mine wouldn't downshift at all.  After I added the split hose, it down shifts correctly ever since.