Check Engine

When I'm driving around and am on the gas, the light is off...when I let off it comes on. Any advice on what is doing it and what needs to be replaced? Also my fuel gauge is def not accurate. I drive around 300 miles and fill it up to be safe. It wont go above a half tank when its filled up. Do I just need to replace the sending unit? Thanks for any advice.

i'm stumped about the EGR light, unless there is a vacuum sensor that is acting weird or loose.
However for the sending unit you might be able to fix it by cleaning off the contact and rebending the arm. I've fixed 2 of these in this method and it works well. One still to this day and the other was sold years ago.