K20a2 Swap Question

Hello a buddy of mine has a civic si 4 door, FA5, it got hydro locked and blew a hole in the motor, he had a spare K20a2 motor laying around and decided to want to bolt that onto the Civic si, will he be able to use the car with the K20a2 Longblock but with RBC manifold and throttle body since its drive by cable and not drive by wire, will the Si work with the stock ecu, or will he need to have it flashed in order to work?

Thanks

K20a2 Swap Question