I'm sure the engine is clean. Aside from the additives in the gas here, I've run BG 44k through it a couple times and noticed no difference. The previous owner complained of the problem to his tech and gave me reciepts when I bought the car for the belt dampener and new injectors. I pulled and gapped the plugs. They are Bosch copper, but aren't worn enough to warrant replacement. All of this and no improvement in the warm idle. Cold idle is good. I am hoping this might also fix the need to start the car twice when it's warm. It will start and die unless I have my foot on the gas. Second time starts and idles fine.

I found the plug in the fusebox, but there are two violet wires, one going into the bottom of the plug, one going into the top. Which of these do I remove and ground?

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Fourings

84 Audi Coupe GT with Turbo engine, EFI (buh-bye CIS), Jamex seats, Koni's/H&R's, e-code lights. 210k and counting.
1992 Anthracite 400E, 161k, "Grey Ghost".
1986 VW Quantum Syncro, 192k, gone to the crusher in the sky.
1989 300TE 172k. (Was mine, now also Mom's car)
72 280SE 4.5 (Mom's car)