I took a look at the throttle friction adjustment tonight. Looks like you have to pull off the black plastic dash/cowl cover to get at it with wrenches. I did take the big screw off the top and got the cover loose, but it looked like a project to get everything disconnected so I bailed since it was getting dark. I did squirt a few shots of lube into the friction plates from under the tractor, and that helped quite a bit. I'll see if that takes care of the problem during operation, otherwise, I'll take another shot at getting the dash/cowl cover off and then adjust the two nuts that control the friction.
I have also been getting a creak from the FEL quick-connect pin on the left side, and a shot of WD-40 silenced that instantly. Wow, that was nice!
I am curious what other 2620/2920 owners are using for tire pressures -- for the R4 tires, the manual says 35ps front and 40 psi rear, but that happens to be the max pressure printed on the tires, which seems odd. Normally, the operating pressure is a bit lower than the max psi.