I've had this problem on and off for about a year. When the truck is cold and after I have waited 30-60 seconds for it to initially warm up. I will start driving and while its still cold it will get to 3000rpms and have no power in 1st. Shift into 2nd and its okay till the 2000rpm range. Then it catches and misses(bucking) until 3000rpm then it quits and runs more or less normally. Shift into 3rd and it is there maybe a little bit but nothing like in 2nd. The problem is temperature dependent. If its warm 80-90* it doesn't really do it. If its colder it will do it every time but maybe not if you have driven the truck before during the day. The last real clue I have is it quits once you've been driving for 2-5 minutes it quits and drives normally but maybe a little down on power. The only other thing I can think of and it may not be related is it seemed to start after I had a block heater installed last winter.

In the last 6 months I have changed plugs, cleaned the maf and put a new air filter in and none of those things drastically affected the problem. Sorry if the post isn't clear I'm just trying to get down everything that comes to mind that might help a diagnosis.

thanks for any suggestions

Edit Also the truck is not throwing any codes