My Ford F150 2004 4x4 5.4 Liter is shuttering around 40 to 50 mph and the tac around 1100 to 1200, it does it on the flats and going up hills, but if I give it gas it goes away. It was put on a computer and driven and the only thing that came up was the fuel pressure dropped for around 40 to as low as 30. I was wondering if this could be a fuel pump problem. Also I get a smell of gas in the cab. Any help out there. Thanks