I think my fuel pump is starting to fail. I have noticed a few times that the engine bogs down and you have to punch the gas pedal to bring it back to life, it sometimes takes longer to start then before, it has no power going up hills. Will a bad fuel pump cause poor fuel mileage? Its not the exhaust because I have just replaced it with high flow from manifold back. Any suggestions or help would be appreciated..

 

Basic tune-up is done, and you are not using platinum plugs?

 

Like DFlintstone said give it a complete tune up. You can also pressure test the fuel system. If you are working on a 99 like you have listed in your signature. Your fuel pressure should be 49psi +or- 5psi. You can rent a mechanical pressure gauge at most parts store and connect it to the fuel rail and we can go from there.