Accelerator doesn't directly correlate to RPMs/speed

My 02 Saturn SL1 acts a little strange
from time to time. It only ever
happens at highway speeds. When I
drive at about 65mph, my RPMs run
higher than normal. I try to keep it at
about 1.8k, but it will be in mid 2s
instead. My accelerator seems to
have different 'stages' to it, such as
foot off is off 1-75 percent down will
cruise me at 65 and high rpms, and 76
percent and up will make it fly like a
bat out of Hell like my foot is hard
down! Its not only annoying that I
have to go either 65 or 100 down the
highway with no middle ground, but it
also kills my gas even when Im just
cruising at 65 since it is revving
higher. I MAYBE got 20mpg highway
when I normally get 33 combined
when it happened again tonight. It
only happens every 2 weeks or so,
weather isnt a factor, and turning it
off/restarting doesn't fix it. I just have
to resign myself into losing money for
that whole day when it decides to act
up. Its an automatic, and 65 is not a
shift point. Can someone help me
figure this out?