I just changed the plugs, fuel filter, and full sea foam treatment about 5k ago. I'm thinking fuel pressure regulator is next. I'll try letting a little refrigerant out as well. Where is the idle air control valve located?

A couple things to add, I have a CEL for low air flow to the egr, need to clean out the tube. Also have a small exhaust leak on the passenger side that seals itself when the engine gets up to temp.