I had to my truck inspected and had my friend do a quick scan to see why the check engine light was on. It's came back saying both banks were running lean. It's been on since I bought the truck a little over a month ago. It goes off sometimes for a little while, but comes back on. I recently replaced the fuel filter and it stayed off for almost a whole tank of gas, but then came back on when I got below 1/4 of a tank and has stayed on since then. It also idles kind of rough when it's cold. Any idea's what's going on?