you could acutally do it in your ecu harness. 12v through 1K resistor to a pin I can't think of off the top of my head, but iirc, it's blue/yellow.

pullup in your harness to 2I. this is the tach wire.

I have no *stock* harness. I've completely re-wired my car from scratch using the megasquirt harnesses (gotta love doing things the hard way.) but i believe you are confirming what i had in my attachment. I'll grab a 1k resistor and give it a shot.

*edit*

Edit again.

Yep works good!

Thanks.