On the 87 300E and 86 300E, I believe, that resistor is located just in front of the fuse box on the driver's side of the engine bay, behind the firewall. It is held onto the low pressure ac line (the one with a blue cap) with a wire tie. Slide the wire and resistor out from under the wire tie; remove the plastic male connector that holds the resistor; cover the remaining female plastic connector on the end of the wire with electrical tape; slide it back under the wire tie on the low pressure ac line. Total time: 3 minutes. Alleged horsepower gain: 11. Do a search on "resistor" to read the posts on the subject.