greasemonkeyjoe,

I have just finished opening up an out-of-warranty ETM. I find that the throttle shaft is supported by two very smooth turning sealed ball bearings. They show only slight carbon dust on the side facing the throttle bore. I have a hard time imagining any circumstance that would occur that would lead to a flat spot being worn on the shaft bushing.
On the thick film throttle position potentiometers the resistance film is work completely through to the backing film at an area that corresponds to the idle or slow speed throttle position. Since this tells the computer where the throttle is, the computer is getting erroneous information.
Unless he has hard evidence otherwise I think this might be another case of the mechanic trying to explain something that he is knows nothing about.

Don "Double L" Willson