2001 Ranger running rough

My 2001 3.0L/6 is a standard and starts and idles fine. When the accellorator is pressed to take off in first gear the engine begins to run rough. As I move through each gear the same thing occurs as the gas pedal is pressed. Engine never stalls out but each gear acts the same and might possibly be getting worse. Could this be as simple as the fuel filter? or possibly clogged fuel injectors? This is a 1 owner/1 driver vehicle and has been a great truck. I also do all my own oil changes and the truck now has 140k miles.

....Any takers on this one??
Thanks.

Have you checked/replaced anything yet? It could be any number of things. First thing I'd do is replace the fuel filter and then run a bottle of fuel injector cleaner -- and I'd go for something potent like the Lucus Fuel System Cleaner or at the VERY least one of the $2 bottles of the SuperTech from Wally World. If that doesn't clear it up I'd check the butterfly to see if it's gummed up, see if I had a vacuum leak, a sticking exhaust or intake valve from gunk buildup... Lots of things to look at. If you're not running synthetic oil then a motor flush may be in order. If you're not due for an oil change right off, check the dipstick and add some Marvel Mystery Oil to the crankcase to bring the level up to normal and change the oil as normal, see if it helps. If you are due right off, see if you can get a 5-minute flush somewhere and change your oil a little early. Have you changed the air filter lately? Check the PCV valve, it could need replacement. Keep an eye on your fuel economy and see if it's worse than usual -- that could mean a vacuum leak or something. Check the spark plugs, see if they're fouled or worn out. Check the wiring harness for arcing, bad wires, or just replace it if you haven't already.

Basically you need to start eliminating some things before we can be much help with something more esoteric. Good luck!