My truck dies when i get to a stop sign. When i have the thermostat in the truck it always dies at stop signs. But when I dont have it in and after it heats up a little it will rev up and stay alive but it seems like a high idle. I have a brand new iac. new spark plug/ wires, distributor, the ignition control module has been test at autozone it was said to be good. any ideas?? its a 91 gmc 1500 4.3l 2wd