Thanks for all the replies.

John M:
I wouldn't say that it goes away after 3min, but it definitely goes away after about 10min. My bet is that the pump is failing internally; if the outer pulley bearings were the problem, I would suspect that it would whine all the time, not just for a second when you get on or off of the throttle.

I don't suppose there's any chance that the internals can fail & not seize the pump/shred the belt, is there?

Is there anyway to disable the electronics on the pump (ie: unplug it) and solve the problem that way??

On the bright side, I don't have to worry about passing emissions in my current location, so a delete is not out of the question. My main concern would be sourcing a belt that fit properly.

johnathan1:
Definitely not the belt. You can actually feel the smog pump vibrate as you tweak the throttle and it whines.

__________________
Currently:
1972 350SL Euro 4spd
1973 BMW R75/5
1981 BMW R80GS
1995 FZJ80 with OM606 Conversion In Progress