First of all, did you buy the fuel pump driver module with the pump? If not did you check your module? It gets a signal from the PCM about engine demands and controls voltage to the fuel pump. I believe it's by evap canister. The only other thing I can think of is your fuel pressure regulator is controlled by engine vacuum. The car stalls on decelleration or when the throttle is closed. There may be a problem with the IAC.
Also for Johnny, a bad or slow pumping fuel pump would definatly show problems at wide open throttle and not just at decelleration. When it's decelleration it's a control problem not the pump.