I have a 1998 Yukon where the idle at rest is 5000rpm . The enigne does not die but I can see the volt meter go low. If I rev the enigne up to 7000 rpm the voltage is fine. I already cleaned the throttle body and MAF and replaced the idle air control valve.
Any way to manually up the idle or try anything else?

I am sure you mean 500rpm and 700rpm...not to be a stickler, but 5000 and 7000rpm are a little high