yea, but from what OP said he really isn't looking for a muscle car. If he already has a car that gets 15 mpg and that "bums him out", why would he want another? Also a modern stock mustang
v8 =/= muscle car. In fact from 2000-2009 it got between 300-305 hp. Thats less than a 4 cylinder sti, with a ton (not literally) more weight and less than great weight distribution. Real, modern american, don't-care-if-i-can-corner muscle cars are the new shelby's (662 hp) and the dodge viper srt (640 hp) and seeing as OP has a $3000 budget, hes not going to be looking at real muscle cars.
Maybe look at a street bike, you could probably find a 2009 kawasaki ninja 650r for close to $3000, and that has 0-60 of around 3.8, and gets 40 mpg on a bad day.