Have You EVER checked Your bikes injection system???? If no from 1991-92, then it very high time to make so with all needeed checks !!! and that list is not so short, like TPS, syncronization, sensor tests, idle Co2 adjustment, injector maintainingetc. etc....
Anyway i quess, that first U have to check throttle cable routing and same for "fast idle adjuster"(called earlier as "choke"), also condition of cables and lubrication of them...... Throttle must turn back very easily and quite fastly also, so dont use too thick lubrications.....
