my jeep doesnt run like it should

my jeep is a 95 straight 6 and I put a 2000 straight six engine in because I blew the 95 engine up and we have everything in and changed the mounts from the old engine onto my new engine and everything as it should be but my fuel pressure was at 19 with my old pump and with a new pump its at 21 and it should be alot more than that I know. and when I hit the gas it will rev up but almost as if its missing. so I need some help thanks