my 94 mustang with 50k original miles isnt getting the gas mileage id expect and is also lacking the power to pass on the freeway unless i floor it

i can have about three quarters of a tank of gas and travel less then 100
miles and already need to fill it up. it also really lacks the power it seems like
it should have especially when im on the freeway going 60 or 65 and need to
accelerate rapidly to pass someone or to climb a hill..... i can steadilygive a
little bit more gas to the pedal and it seems to me it kind of bogs down or just
has a hard timeaccelerating unless i almost floor it and it down shifts and the
rpms shoot up and then it actually will move a bit faster, but with just 50k
miles on it as well as a brandnew tranny it should run a lot better in my
mind.... does anyone know of a problem that it may be experiencing or is it
just the way that the ponys in the 90's performed and i am expecting to much
out of an older ford V6?