My buddies Cherokee was cutting out bad on the highway for him so he replaced plugs, wires and fuel filter. Ran it for 2 days no prob. Now this morning he was going downhill just barely on the throttle and he felt it "pop" n he could feel it in the pedal it was like cutting out again but not nearly as bad as before. He put it in neutral coasted for a little then put it back in drive and drove home like nothing ever happened. Any ideas on what it could be? Fuel pump? Tps? Any feedback is greatly appreciated.