I have an L67 in a Fiero and I'm using a 95 Bonneville ECM. I installed a Proform shift light and all was well until I decided to change over to a VDO tachometer. In order to get the VDO tach to work off of the Bonne ECM a friend of mine whipped up a little circuit( seems the VDO needs a 12v p-p signal and the ECM gives a 5V p-p signal). The circuit is an npn transistor with the ECM signal going thru a 470 ohm resistor to the base. 12V thru a 1000 ohm resistor to both the tach imput and the collector and the emitter to ground. The circuit makes the tach work great but now my shift light won't work (light input is tapped into the white wire from the ECM before it hits the circuit). If I disconnect the tach the light works. I have talked to both Proform and VDO - Profrom has no clue and VDO is "working on it". Any ECM/ Electronic gurus on here have any ideas.