Had a lifter and rocker arm going out on my drivers side bank, which caused my cat to get plugged. I replaced all the lifters and rockers truck fired up and purred great. Then after a test drive got a p0171 code and was bogged way down under load. Local mechanic said my cat needed replaced on the drivers side. After getting it back from the cat being replaced truck runs better but still getting P0171 (bank 1 lean code) and when accelerating reminds me of my old truck with straights on it and slightly bogged down until getting around 3000 rpm but still sounds like it has straights on it. If i just put the truck in neutral i can rev the engine until 5000rpms with no straight pipe sounds or anything. Any ideas what to check next?

2004 F150 5.4 Lariat 4x4

 

Well newbie mistake on my part. I thought bank 1 was drivers side but its actually the passenger side. I checked the vacuum on the passenger side and the green locking ring was broken on the line to the valve cover. After fixing that all running better. Also on a side note had issues with rough idle and saw someone said something about replacing the foam seal on the filter box around the bottom and after that no more rough idle. amazing what alittle foam strip can do for engine performance.