Sounds like it could be the idle portion of the switch that you are talking 
about.  If that sticks and stays closed when the throttle is opened,  the 
engine will seem to hunt until it reaches a point where the deceleration 
fuel shut-off is bypassed at around 2500 RPM. Try adjusting it. Bentley 
covers it.

Craig Rogers
Ineffable Audio Unity Inc.
P.O. Box 512
Riverdale, NY 10471
(914) 378-1606
mailto: carogers@idt.net