We did not increase the ground speed in 2010. We did improve upon a number of the components to increase their resistance to wear. I believe that you are just a little out of adjustment. The threaded cable you referenced is an adjustment. Page 41 of your operator's manual has instructions on how to adjust the tracking. If you still feel that you need a little more ground speed, you can also gain ground speed by adjusting the neutral position of the control handles. Page 49 of the operator's manual covers this. At step #2, adjust the RH control handle so it is to the rear of the neutral slot vs. the center. It still must move freely into the slot, as this is your "operator presence control" or "dead man switch". By moving it rearward, you will increase forward ground speed with the additional control handle forward stroke, but will give up reverse ground speed. After adjusting the neutral position, your tracking may need re-adjustment.
The Toro Company