I have a 2002 Taurus and my fuel pressure varies. Some days it runs and accelerates great. When I check the fuel pressure it is between 50-55 psi. Sometimes when it bucks on acceleration I go home and check the fuel pressure and it reads from 24-40 psi. This happens quite often.

I would think it is the fuel pump but I don't want to replace it if it is not the problem. I also suspect a bad fuel pressure regualator but it is not on the fuel rail as in previous years. Is the regulator built into the fuel pump. When I look up the regulator on Autozone's webpage it does not show one for my car. Any help would be greatly appreciated. Thanks

 

Don't know just how much help this will provide, but may clear up something.
I believe The fuel system on your vehicle has what is referred to as a returnless fuel system. That means there is no return line coming from a fuel pressure regulator that used to be located in the engine compartment. The pressure regulator is now part of the fuel pump module in the fuel tank. The fuel pump is controlled by a pulsewidth modulated system where the fuel pump runs only when necessary and can have different pressures as long as the engine is supplied with the amount of fuel actually needed.
There is still a filter in the line and do you know if that has been changed recently? It might help if you had Autozone check for any codes in the computer. It might provide some direction.
There should be a fuel pressure sensor on the fuel rail that is supposed to tell the system if more pressure is needed.