Any one really will do since you are only really looking at DC Voltage. First you measure the voltage at the battery with the engine running and up to 80 degree operating temp! Then you check the voltage at pin three on the X11 connector on the left fender well. Next it should wander up and down a bit, you basically want the center point of the wander to be half the battery voltage which is a %50 duty cycle. Less than half is running more rich and toward less than %50. More than half is lean. Some people say for better response to run at %45 or less. That would be a hair lower than half your voltage. After each turn of the allen key, small bumps not anything big, you need to blip the throttle and wait for the reading to settle again. That is really all the is to it!

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....