This is very common in old Vanagons.Not much you can do.Nobody will re
bore the shaft holes and put a bearing in.Tolerances are just too close.
Off by a couple thousands and your butterfly plate will bind. Best to just
readjust your throttle switch, and move on to the next problem.Perhaps a
weaker return spring will not pull the shaft off center as much.I do not
think a new throttle is avaliable,new.At least not for less than $500.