Fuel System Problem?

TJ 4.0. When im driving at a steady speed the engine lags and it seems like its not getting enough gas to the engine. The problem only lasts for about 15-30 seconds and stops. If i stop the car the engine shuts off. Downshifting seems to help a bit. This doesnt happen all the time and seems to happen after about 20-30 mins into driving. could it be the fuel pump, fuel filter not sparking right? any comments would help me alot. thanks

what year is this tj, first thing I would do is check if there are any codes stored in the compter, AutoZone will do a scan for free I hear. I'm in Canada, we don't have anything like that here. There could be a code stored and you could pin point it right away instead of guessing and spending money for nothing. Year and milage would be helpfull.

its a 2000 with 91000 miles. today its been acting up alot worse. when u hit the acclerator it hesitates and chugs.