I had an intermittent bouncy idle when warm, and found that not all of the various throttle linkage bits were returning to their proper idle state. Some of those little nylon rollers were binding, and one of the "hey, I'm in idle!" micro-switches was not being activated.
It was intermittent because if the pedal was let back with enough momentum in its favor, the linkage would return to the stops. If it was let down easy, it would stick.
Cleaned and lubed every moving part on the linkages, and the problem cleared up. I used white lithium spray grease. Others prefer ATF for this.
If you are lucky, this low cost/low tech 'black box' approach will work for you too!
1986 300E 5-Speed 240k mi.