Fuel system?? Help

I have a 95 jeep xj cherokee. My engine runs fine unless I have been driving at a consistant speed of 70 mph or higher for more than 40 minutes. The motor will seem to "hiccup", or have a very quick and jerky lapse in power. If I accelerate or decelerate it discourages the problem, and the longer I drive worse the problem becomes (in frequency and in intensity of 'jerk') Also, after the problems start at high speeds after the 40 minutes on the highway, it continues at low speeds.

Then engine temperature has nothing to do with the problem, nor does the length of time in which I have been driving. If I am offroading for hours, or driving at inconsistant speeds there is no problem.

I replaced my fuel filter and the problem seemed to lessen, but it is definately still there. I'm guessing the fuel pump is failing, anyone have experience with this?

thank you so much for your input.

im not exactly sure what your talkin about but i had almost the same problem i t hink ur describing, i was drivin down the road at a constant speed and it stopped recognizin i was on the gas it felt like, anyways it ended up bein the tps(throttle position sensor) i replaced that and it was fine. not sure if thats wat your problem is but sounds like somethin that happened to me