My nieghbor has a 04 that has started sputtering at take off and sometimes when he comes to a stop. Had the fuel filter changed. Mech told him there was some water in canister filter chaned it. truck ran ok for few weeks now doing it again. he drained the water separator but did not get any water in drain pan. has ran couple gallons of all kinds of fuel adds thru truck. Any Ideas?? He has no guages. I told him at least needed fp guage.