Car stumbling on acceleration and surging

My vehicle will start up fine but as soon as I get out on the road driving it will lose a lot of power and sound like its backfiring. After a few seconds it will surge forward like it got all of its power back. This happens anytime I want to accelerate unless I floor it. Also when it is running at road speed it seems to run a little rough and it lacks power anytime I have to go up a hill. I've already replaced the fuel filter, fuel pressure regulator, and fuel pump. However with the fuel pump when I replaced it it was with a Warblo High Performance pump and all it did was buck so I put the old one back it and it stopped bucking but the old problem was still there.