Truck has a chug and high idle after it warms up. If it's shut off and let sit for 20 or 30 minutes then restarted the chug is gone and the idle is perfect. Checked and cleaned the EGR, replaced the IAC, checked the TPS, replaced vacuum lines, replaced ground battery cable, distributor and wires are pretty new. Kind of lost to what it could be. What tick mark is 6 degrees for the timing? When I unplug the IAC there's no change in the idle. Any help is appreciated.