XJ8 2003 loud whistling in the back

Hello all
I recently noticed a continuous, rather loud, whistling at the back of my 2003 XJ8
I thought it was the big back speaker gone bad, so I went to the trunk, got access to the plugs and unplugged it…
The whistling has not gone and it is actually louder in the trunk
It looks like a pressure/electronic high pitch hissing from the tank sender unit.
Has anyone ever gotten that ??

Could be the fuel pump DYING from a clogged fuel filter??


Oh I have to check that