Is it possible to re-program computer for better mileage?

I have a 98 Silverado with the 350 Vortec. The engine runs great, but I would like to improve the gas mileage. Is it possible (or advisable) to re-program the computer for better mileage? If so, would anyone know where to buy a new chip, or have my current one re-programmed?

I don't care if I lose a little power. This thing has way more power than I need.

Thanks

I know that dealers usually receive updated programs to improve driveability. You can call them up and see if there are any updates. Should only cost about $100 or so. Also it would help to get a cat-back exhaust, and a better flowing air intake. Even just replacing the air filter with a K&N filter would help.

Hey, I'll trade ya my 4.3L for your 5.7L!! Gets about 20 mpg, and still packs alot of punch for a V6!!