Response, Gain, Idle, Option Out (not normally used)
It's best to just leave everything at zero and use a piggy-back fuel controller such as a SAFC. The VPC has limited adjustability.
IIRC Response will add or subtract fuel on initial throttle opening only. Gain will add or subtract fuel across the board and Idle is just that. Adds or subtracts fuel only at Idle. Option out is for an FCON which is not available for a U.S. spec Supra.
Hope this helps.