I got around to replacing my faulty Throttle Valve Switch (TVS). It required pulling out the throttle assembly, which is held in by four small Allen-headed bolts (and a fused gasket). Once out, it took longer to clean the tar-like goo coating the underside of the butterfly than it did to swap the TVS. If anyone thinks it useful, I've posted a new thread with the details at The 560SL Throttle Valve Switch Replacement Narrative. On hindsight, it wasn't too hard. My idle speed has improved (read dropped), but is still not down to the target of 650 rpm (more like 950 for me now).

ctaylor738, the big hose clamp holding the Air Guide throat onto the throttle body broke the moment I tried to tighten it. I can't identify this part or find it on a cursory search at Fastlane, ******** or PerformanceParts...any suggestions on a source? I'm starting to look for a generic hose clamp equipped with a side-ways screw setup.