Sorry, you already mentioned that. From what I understand, the Engine while cold takes readings from the ECT, Airtemp, Map and the TFI at start to set the Cold Crank Scenario (Closed loop, computer controls timing and uses preset fuel ratios.). Then after it warms, it starts to read the O2 sensor and switches to an Open loop (Sets timing and ratios by the sensors) to control the idle/Fuel Ratio. Which is a warm cruise scenario (Cant remember the name actually). In conclusion, if its running like crap while its cold, first start of the day, then you either have vacuum issues, or could even be a lack of coolant in the system, so your ect doesn't get a correct reading. That's what I love about these trucks. It could be anything. One piece out of place and it runs like crap but alls good and it's a great little motor. I hope that helps.