I noticed this a little before, but today it really showed its face. Sometimes while driving around it seems like it takes more throttle than normal to hold speed. For example, today coming home from work I had to hold the pedal just short of the floor to hold 70mph. At first I thought it was just the wind because it was very windy but after I stopped, filled the truck up, and got back on the highway it barely took half throttle to maintain speed. This is with a rebuilt engine with approximately 5,000 miles on it, and all of the sensors were replaced except for the TPS and EGR. The motor has never run bad and gets great mileage for winter. So, what would cause such a drastic difference in pedal position?