Well the tach sensor or possibly the Cam sensor is the round up right electrical part. Looks like a port for a computer to be plugged into. Mine is on the drivers side fender well just above where the Cruise control actuator plugs into the electrical connector.

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1986 Euro 500SEC "RUF" 9:1CR, "Rose"
1985 Euro 500SEC Cabriolet AMG Widebody
1982 Euro 500SEL "Blue"
2001 Texas Heeler (Aussie/Queensland X) "Sulphie",
2012 Queensland Red Heeler "Squeak"
Best dogs I've ever had.