98 expedition acting up

ok on my wife truck it acting up se said it feels like it running out of gas but has plenty one time it happend going up a hill so she gave it more gas it strugeld then took off the next time she was coming to a stop. she then completed her stop and it took off fine.so im kinda stumped on whats wrong and i really dont want to take it to the shop. it only happed them two times. and its only does it so far once a month.both on nice day around 70* or so

Mileage? Is the Check Engine Light on? When was the last time you changed your fuel filter?

298,000 and as for fuel filter ive never changed it but ive only had it two months. they guy befor me has had it changed a few times real anal about up keep on his truck.