[s-cars] fuel supply question

[Rokas Reipa]

Hi folks,

Have a question that's been nagging me for months now, if not years. My 95.5
S6 seems to accelerate faster and generally feels peppier when the gas tank
is half-full, rathen then when it's full. When the tank is full, it
sometimes feels downright lethargic and livens up like clockwork right
around when half of the tank is empty. Apart from the obvious weight
reasons(a half of a tank doesn't make that much difference anyway, right?),
is there a scientific explanation for this? My old 1986 5kcst did the EXACT
same thing and I could never figure it out. Is some fuel delivery component
on its way out? Thanks for your help,

Rokas
95.5 S6