I hope I dont jinx myself, but its been three weeks now since I replaced my thermostat. I had the coolant temp code and have been fighting the 71/74 lean codes forever. So far no lights, no pending codes, car is running smoother, gas mileage improved, suction at the oil filler cap is barely noticeable. I am guessing my thermostat has been failing for some time, engine not getting hot enough to keep the mayo out of the ccv. Seems like all is good for now. What a battle this has been!