Why does the fuel pump fuse keep blowing on a 2003 mustang gt? on 2003 Ford Mustang GT

I have changed the fuel pump, the relay and the constant relay. Paid a mechanic to fix it but he could not.

Asked by for the 2003 Ford Mustang GT
TO MUCH RESISTANCE IN CIRCUIT. CK FOR CORRISION ON PLUGS AND WIRING AND ANY OTHER CONNECTION
It's not that; I've checked all wiring and plugs. Any other ideas?