I'm searching for a car which is both fast and gets good gas mileage. What are some cars that are really good on gas when you drive them lightly, but can really haul ass when you floor it? Also it has to be brand new. Any ideas?

evo, sti, audi's, is300, heck i dunno. most brand new cars when driven lightly get good gas mileage regardless of engine size

evos hardly get "good" gas milage, 14-15 average

srt4, scion tC

Weight reduction, RWD, and low cam overlap.

That means, power production at low RPMs, RWD so you can actually use the power you're making, and reducing as much weight as possible. Although low weight won't help much with mileage, it will help you accelerate faster within the same efficiency.

Turbos are great for this goal.

Look to MR2, Z4, M3, C5 corvette, or Miata with mods.

You said no V8s... you're seriously limiting yourself by saying that. The C5 vette's are getting over 30 mpgs depending on driving style. My uncle drives his to work everyday; not even highway, and he's getting the same mileage as my wife's Tercel.