How far up in the tank does the o-ring sit? I'm thinking if the sound is there with a low tank and not there with a full tank (the leak is submerged) you guys might have the answer, I just filled up so let me go listen now to see if the sound is still there.

1995 Talon TSi AWD
Evo III 16G / FIC 850's / Walbro 255 / RTM FMIC / ECMLink V3