Here's the next chapter in this frustrating story. At operating temp, with red in pin 3 & black grrounded via the strut metal (I got a fixed 90% reading when the black was in pin 1) , the duty cycle fluctuates around 22 %, and when I revved the engine via the linkage it was around 56-64%. At idle, turning the adjustment screw did nothing. I was reading the Haynes manual & wondered whether the microswitch/accelerator cable connection might need to be adjusted. Also, this car used to be pretty quick, & now I have minimal pep & its very hard to get over 40mph. Any thoughts guys?

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87 300e (white/black; amg body kit)
88 300ce (red/cream; amg body kit)
93 300ce cabrio (white/blue/blue top)
93 300ce cabrio (black/grey/black top)
98 ml 320 (totaled @ 137,000 miles)
99 clk320 (black/grey/black top)