I just switched from a 1996 thunderbolt V ignition to a DUI hei ignition. Q: I have a wiring diagram that says to use the grey wire from the wiring harness and hook it to the tach. I did that but the tach will not work.

call them, should work fine...used them before...

Anyone ever make this switch?

It should work, 2 wires to the coil, B+ and tach, not sure of the colors. If I get to the boat I will let you know what color wires I have.