Are you sure you are getting a vacuum in the tank?
I ask that because my tank is always at a small positive pressure - when I take off the cap at the gas station - pressure escapes.
I am convinced (well 99.9%) that having a pressure in the tank is the normal condition.
I realise we are on different vehicles here 123 v 124 but I would not have though fuel system would be that different.
From my owners manual page 164
Prior to refuelling, turn filler cap to left and hold in position to allow excess pressure to be released.
Hope this is helpful.