Engine Problem

[K-Mart]

I have a 03 GMC 2500HD with a 6.0. Every time winter rolls around the truck starts to act up and wont rev past 3 grand or sometimes even 2 grand. It seems to happen only in the winter when its cold but get worst went there is moister in the air. I have changed spark plugs, wires, coils, injectors, MAF, throttle body, 02 sensors and has no cats and has been tuned to run with no cats. i have checked all grounds and seem to be fine and its not pulling up any codes. Has anyone else had this issue?