95 Ram surging intermittenly

[tuthleselk]

I have a 1995 Ram 1500, 5.9 L, This truck has a surge in it every once in awhile. Mostly what happens just after I start it and begin to go down the road it begins to surge like it is running out of gas, usually it only lasts for a hundred yards or so, then it staightens out and run normally. Sometimes it is everytime I start it up and then sometimes it goes away for a few days or so, sometimes when the engine is hot and sometimes when it is cold. I do get a code 21 sometimes also, which has to do with the oxygen sensor not fluctuating. I have a new oxygen sensor to put in it this weekend. I recently have changed the plugs, wires, dist cap and rotor and coil with no change in the way it acts. It really has me stumped, my mechanic friend put a fuel pressure tester on it for a few days but it didnt act up at all when that was attached, thanks for any help you can give me

No matter where you go there you are!!

[tuthleselk]

it actually acts like it needs a new fuel filter, or like it has dirt or something in the tank blocking something, really confused!!