If the tank lid is right in place in the fender, you don't want to change a single thing to it.
If you remove the top of the fenders inside upholstery at the tank lid side, you will find the vacuum pump for the tank lid (round black pump with steel pin and red plastic top) which is screwed to a thin chassis part.
Loosen these two screws and shove the pump up or down whilst trying the lock by pushing and pulling the red top.
Tighten the screws when you have the pump positioned in a NO-noise way.
If this is not sufficient you can twist the steel chassis part on which the pump is mounted on. Do this gently and nice and it will help as much as repositioning the pump.
greetingz & good luck
with a minor 600+k