Accelleration problem

Ford f150 4x4 auto 4.6. Just did a engine transplant. Has 32000 miles on it. Getting a knock sensor fault 0325. No other faults. Idles and runs smooth unless you accelerate hard. Then it bucks as if plugs are foulling then clears. No check engine light. Have cleaned maf changed injecters. Only does this after it is warmed up.