I got a MSD RPM activated switch with a 5800RPM pill so I can hook them up to the secondary butterflies on my GSR manifold and I'm trying to get the wiring down. I got the following hooked up:

Red: power
Black: ground
Gray: ground for butterflies
White: DONT KNOW WHERE THIS GOES, but it's for the RPM input
Yellow: not used, correct?

Basically, I tried hooking the white wire to the same blue wire that my shift light is hooked to, and it didnt work, PLUS my tach wouldnt move either. So where do I hook up the RPM wire too? What is the wire color in the engine bay? If need be, I can post pictures. Thanks.

 

Its made to be used in conjunction with an MSD igniton box, or an MSD signal amplifier, the white wire plugs into them. The switch you have draws the all the voltage for itself and doesnt share. The MSD boxes have an output for them the signal amplifier just makes the signal stronger with no ignition system gains.