[graymarki]

First thing I would do is take a fuel pressure check. If your gas mileage was OK, before the first mechanic replaced your pressure regulator, than most likely it was not the immediate problem. It's fairly easy to check the fuel pressure as the fuel rail has a screw on, or quick dissconnect on top for this purpose. Secondly, you failed to mention what engine you have in the car. If you are not mechanically inclined & cannot do a pressure test yourself, then find out what the fuel pressure should be for your particular engine. Look in a manual, ie. Autozone, or ask someone. If your pressure is too high, I would have the first mechanic replace your old pressure regulator and see if that solves the problem. Many things can cause higher fuel mileage, bad oxygen sensor, bad tcc solenoid in transmission, dirty fuel filter, spark plugs, dirty throttle body, or a bad sensor sending the wrong info to the computer.