Some ideas,
Run a injector cleaner and clean the air filter.
Reset the ECU after
Put some Silicon spray/lubricant on the Throttle cable and give it a clean. Check its not getting caught (I know you have had a look but that is what happened on my 1990 one )
Is it an after market Cruise control, if so they are evil
Check your accelerator in the car can it be pulled back from idol a bit?
hope that helps.