Lack of acceleration

Car ran great until I got gas one day, backfired about 2 blocks from station.
Light came on pulled codes and replaced the throttle position sensor. Light came back on and now slow take off but will rev to about 4500 then lays down.
Pulled codes and replaced the fuel pressure regulator. Still no acceleration. Can get the car to highway speeds no problem, but try and pass anything and yup lays down. Have to take time to get up to speed. Exhaust pressure is fine, idle is fine, and runs fine, until you try to get moving.