It only does this in the winter when i run it hard. It has done it once during the summer, but its not as common as the winter. It runs like a top otherwise. I have not changed the fuel filter. the truck had 5k on the rebuilt engine at the time of purchase and the previous owner claims to have went through everything in the truck, but i have found he lied about a few minimal things. Once shop room opens up I will look into the filter and see if its fuel related. Thanks!