Well, I will try and keep this as short as possible. 1st. My truck is a 2010 F-150 XLT Screw with the 5.4l engine. Roughly 2 months ago I purchased an Injen powerflow CAI, AIRAID throttle body spacer, MBRP stainless cat back system and a Hypertech Max energy programmer. After installing everything except the programmer, I started driving the truck and noticed that my fuel millage was terrible(I wasn't driving it hard). I figured this could have just been because I had the battery unhooked and the computer had to "relearn" the fuel trims. So after driving the truck for a couple days I installed the programmer and was not happy with it at all, and within another couple of days I returned the truck to the stock tune. It has been about a month and a half now and I still have all of the other Mods installed except for the programmer and my fuel Millage is still not great(23L/100km). Just yesterday I read online that while the truck is in the "relearning" process, it has to be above 5 degrees Celsius outside(it was about -25 degrees Celsius when I did it). My question is, would that have any affect on how the truck "re-tought" itself? I would let it warm up for 10-15 mins before driving????? Or is there another explanation??? Please explain, it would be greatly appreciated!!