My 2003 ( no mods except fass) runs great until I fill er up. Then it lacks power. When I get down to a half tank or so it runs good again. I know there were other threads here talking about this problem but I found no solutions to the problem. Sounds like a venting problem to me or?

 

Check fuel pressure with a full tank, then at half tank and compare. You can also vent the tank by removing the fill cap and see if that helps. Plugged or restricted fuel return line will also cause a lack of power.

 

The return and fuel cap checked out ok so I went to the next possible item on the list ( crossover tubes) Removed all the injector feed lines and checked the crossover tube hold down nuts. Two of them were torqued to about 10 foot lbs. I pulled the tubes out and scotch bighted the ends re-installed and torqued to 37ft.lbs. That was the problem, the truck runs great now. Thanks hvytrkmech for your advise!