Need some help. Recently returned from a drive from Eastern Nebraska to SW Colorado and back for Christmas. Car did great the whole drive until the last fill up coming home. That last tank of gas resulted in 17mpg and the car would not hold cruise anymore. At first I thought it was because I was driving into a head wind, but the drive to work and back last night the car was doing same thing. You have to go into boost to maintain speed going up hill. Never had to do that before. Its almost like there is something holding the car back. Acceleration from a stop seems normal. Goes into boost, will spin the tires, blow off valve functions. Might take a little more pedal to get up to speed, but really hard to tell as roads are crap right now. It was like a switch got flipped with that last tank of gas on the drive. When you try to set cruise, it won't hold the speed and seems as if the cruise is surging trying to. Like it will pull on gas, then let off all the while the speed keeps dropping. Used to be able to pull up hills and not have to get above 2psi of vacuum. Now I'm having to get 1-2psi into boost. And I have filled up with fresh gas last night so I don't think it's the fuel.