well first do a complete tune-up(wires/plugs/oil/fuel filter) the whole nine even the coolant if you want. [[[ ALSO:buy ngk plugs and wires ]]]
then you check for probs.
TPS MAYBE OUTTA WHACK if problem maintains after tune-up
if there is still a prob after the tps which i doubt there will be then post up
hope that was helpful.

also these rotaries go thru plugs like they are goin outta style so maybe every 4-6 months they should be changed unless rode on hard then change them maybe every 2-4 months