What was found
FLT 31, JFK-MCO, JUST PRIOR TO ROTATION SLIGHT ROLL BACK ON NR 2 ENG. ENG MADE COMMAND THRUST, AFTER LIFT OFF, THEN ROLLED BACK TO 31.3 N1. RETURN TO JFK. UPON LANDING ENG 2 NO DISPATCH. THEN ENG, FAILED AFTER CLEARING RUNWAY. YAW CORRELATED WITH ROLL BACK. REMOVED AND REPLACED FMU IAW AMM CH 73-21-03. OPS & LEAK CHECK GOOD. AS PER ENGINEERING REQUEST REMOVED AND REPLACED NR 2 ENG FADEC AS PER CF3410E ENG MM 73-00-00-800-812. OPS CHECK OK.