Sluggish Acceleration

Anyone have any ideas as to what could cause sluggish and jittery acceleration when you floor it from a stop? My jeep seemed to be struggling with the bigger tires on, and I think it may have to do with TPS sensor, since the tranny shifts hard into second gear. Any ideas? It's an AW4 tranny, and I just find it weird that it's happening all of a sudden when it never would before

Do you experience this just during a hard acceleration from stop, or during acceleration on a cold engine?

Usually just from a stand still, sometimes while rolling at around 5-15 mph

are you running the stock gears?

Yes, I am. Doesn't have much to do with it though, since i've had these tires for nearly a year, and this is the first time that it's happening.

Sorry to hikack this thread, but Im having the same problem too. I just did a complete cooling system overhaul(radiator, electric fan, water pump, thermo.), free flow cat, and a homebrew air intake with throttle body spacer in my 98 4.0 Cherokee. It now feels very sluggish, Im thinking its running lean because of the intake mods. Do you think a map adjuster will fix the problem?