follyburr

my car has 200k miles, 5sp. My car doesn't get great mileage. I figured it was due to one of the cats starting to fail. p0420 code. However, i my gas needle seems to never be in the correct position. it will be at one position then drop about 1/4 lengths and eventually go up when i the car faces a different direction(downhill, uphill, etc.) . Would replacing the fuel pump assembly help with mpg and fix the needle issue? THANKS!!