10k Resistor Mod?

[RustyBolts]

I was poking around Youtube a little bit ago, and ran across several videos about people doing a "resistor mod" of various resistance values (1.5k to 22k), giving their trucks a lopey idle, and making them smoke.
My questions:
1. Where does this resistor go?
2. What does it do?

 

[Mike]

It goes inline with the ICP and it fools the PCM into believing the oil injection pressure is low so it ups the duty on the IPR.