Tuner as Commuter Car

I need some help. I got a job and am about to graduate college. However the Job is on the other side of 495 and my current vehicle is a Chevy Silverado with the works so gas consumption is bad on it. So i want the truck to be for in town and to purchase a tuner to commute in. My question is what would be my best bet on MPG while being a fast and fun car I can mod out while still not guzzling gas at 12-15mpg like on my truck. I was looking at an eclipse GSX but still have no idea what year to look for etc. Help me out please.  

the first gens are better, but because they are over 15-20 yrs old, it will cost some money to get it running good. the second gen is good, but can suffer from crank walk. imo, get a third gen. 03-05 gts. with a few mods, i have 190whp and i get 32mpg on the highway and 25mpg in town.  
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the godfather has spoken
R.I.P. GRANDPA PITT AUG 10, 1930 - SEPT 30, 2010

AW11 MR2's can get anywhere from 25-35mpg, but same deal as the older Eclipses, older cars and hard to come by in good shape.  Good luck.  

Generally, faster cars will eat up more gas. If you want something peppy that's decent on gas look at something like a GSR/RSX type S.  

Depends on your setup, roots type superchargers can be turned on/off for power/fuel economy.  It depends on your setup and how you drive.  But overall I agree that higher performance leads to less gas mileage.