I have a '97 4.6L F-150, ext cab w/ offroad package. I just had headers and a new muffler installed on it not too long ago. Ran fine for a while, then out of nowhere it starts sputtering when I give it gas. Its still driveable, but I can't for the life of me figure out what's wrong with it. It almost sounds like its misfiring, however the check engine light has not come on (and I know it works, because thats how I ended up with a new exhaust). I'm going to try resetting the computer tonight and see if that helps. Also, I plan to change the spark plugs/wires and the fuel filter this weekend at the latest. It needs to be done anyhow. It's got 125,000 on it and goodness only know when the last time either of those was changed. Any other ideas on what could be causing this? Thanks!