I hear a weird whining noise coming from near the gas tank every time i turn my car off and my gas tank has a lot of built up pressure when i fill up and it seems to be using up more gas than usual

 

mine did that too i always thought it was the nature of a high pressure fuel system
ever heard of the "dont use cheap plastic body fuel filters on 90's nissan"
although i always wondered if my evap system(aka charcoal canister and vac lines)