Could very easily be a very clogged filter. Start there, if that doesn't fix it then:
Check your plug wires, make sure they dont have any frays, cuts, tears, or rust on the inside of the boots.
Check your plugs. Check for cracks in the porcelain, and see if they are properly gapped, and not fouled.
Check your coil packs for rust on the terminals, or any cracks/splits in the coils themselves.
If it feels like your hitting a wall during acceleration (doesnt want to go over 4000rpm or so) then it's most likely the catalytic converter.
If you're still lost, get the OBDII codes pulled, and see which cylinders it is misfiring on, and go from there. If it comes back as a "Multiple Cyl. Misfire" it more than likely a bad coil pack.