Please any help will be much appreciated. My 2008 Ram 1500 5.7 4wd is having issues with the idle kicking down from 600 to 500 when I come to a stop at a light or stop sign, I noticed when I turn the dial for the bent position either from defroster to vent or vise a versa it kicks back to 600 rpm where it should be. And I have a problem of when I fill up the gas tank it shuts off. I just replaced the Evap Canister, Evap purge solenoid, crank shaft position sensor, map sensor, air inlet temp sensor, EGR Valve, cleaned the throttle body, and changed the PCV Valve. I'm racking my brain of what can be causing the RPM draw and then kick back to where it should be at 600 RPM. Any help would be lovely please. I'm stumped and frustrated. Thanks for your time.