5.088lxdood87

I drive a 1988 mustang 5.0 lx and im experiencing some humming noise coming from the back passengers side im thinking it could be a fuel pump problem and it has been pretty consistent with doing it and when i put my car in reverse and drive the rpms flutter down to about 500rpms and the car dies out im not really understanding this ive heard 50 million different reasons so im just trying to get a little bit more advice on the issue thanks for the help guys!!!