If none of the above suggestions work, try this - cheap & quick, might fix it.
Turn ignition on, roll throttle to wide open over a 5-count, hold it for another 5-count, let it snap closed,. then turn off the ignition.
The computer sometimes can forget what the values it sees for closed & wide open throttle are - this reminds it.
If this doesn't do it, I'd start looking at either the throttle position sensor or the rubber throttle body adapter - it can crack / split with age, totally screwing up your fuel / air mix.
'99 V92C with K&N, PMRT chip, Vic stage 1 slipons, and engine by Rylan Vos!