Wait, why is the convertor even there when the ECU gives out the rpm? When the ECU gives out the correct rpm, based on crankshaft sensor (so not coil firing) then you wouldn't even need the convertor, right? Also, I thought the convertor was just to change the frequency from 6 to 4 cilinder, not an amplifier. Thinking of that, if the convertor is made to change 6 to 4 cylinder frequency for coil signals, it might even not respond to the low voltage coming out of the ECU. Edit: I just realized the signal from 4 cylinder is also double the rpm, when coming from the coil. My KMS computer also puts out a 4 cylinder signal, so doubles the RPM, and the tacho gives the correct RPM. The KMS is programmable, I reccon the ECU of the VR6 engine isn't? So it depends how the 6 cyl ECU puts it out and if there are differences in the tacho's for the 4 and 6 cylinder cars (from the age this engine is). That kind of things I don't know, but now I'm curious how this is handled!