I will be putting a 305 tpi out of a 91 z28 into an 86 iroc. My question is how is the vats system going to work? The 91 ecm will utilize it, but the ignition isn't equipped for it. I have no way to find out what kind of resistance is needed as I don't know where the donor car is.

 

Vats came wth 15 different resistors, you could just try each 15 out and solder the right one in the wiring. and youre good to go.. just buy 15 resistors with this values :

 

Since your car did not come equipped with VATS, to do the resistor mod you would need to procure the VATS module and wiring. A simpler approach in your case would be to disable VATS in the PROM.

 

Yeah, but in 1986 there is no VATS activated in the PROM.
It didnt came until 1989 as standard in the Camaro.

 

He's using a '91 ECM which his '86 PROM will not work in. If he was using an '86 PROM he would not need the resistor mod.

 

Sorry for that, Then he need to diactive it in the prom.
This isnt 100% failsafe, VATS could be a problem, the best way is to
solder in an resisiter in the wiring (instead of on the key) or disable it by taking away/remove/disable Starter enable relay, VATS fuel enable relay and the passkey system then you dont have to worry about VATS being a problem.

Info about how to disable VATS completly : www.vatssucks.com