Resistor wiring

if you are drawing low currents, ie reference voltage you could use a voltage divider, ie for 12V supply and 3V output you could use 1:3 resistor ratio ie like 1K, 3K... (1k will have 3V on it, 3K will have 9V on it)

but this is probably not what you want, we really need more information to provide any useful advice.

Just to let you all know... I figured it all out- VTEC engages in a B18C integra GSR engine @ 4400 RPM under optimal conditions, in addition the IAB (intake air bypass) valve switches over at 5800 RPM (always) This 2nd process is the more noticable audible and physical alteration that you are all familiar with in VTEC engines.  I simply installed another LED onto the IAB wire (Pink with blue stripe for those who want to do the same thing) and I now have a single red LED when VTEC engages staying on all the way through VTEC and 2 blue LEDs that light when IAB Switches over (at 5800 RPM), which remains on all the way through redline also.... for those wanting to do this, I used 18 gauge wire, 1.5-1.7 Volt LEDs with 20Ma  using a 360 Ohm 1/2 watt resistor-

If you want to use more than one LED like i did...  Just wire them in series... 12volt + to + lead on LED, - lead to LED to + lead of 2nd LED, - lead of 2nd LED to ground...etc...

Mike