Chip for more MPG

Does anyone know of a chip or something you can do to get better mpg on the 5.3 ? I thought there used to be a guy that would send you a programmed chip and you had to send him yours back.

http://www.nelsonperformance.com/
http://www.gowheatley.com/
http://www.wait4meperformance.com/

And I'm sure there are others out there...

hyper tech power programmer. you can fine tune for gas type, rev limits, shift points...
works well in my '99 4wd, get 20 mph on the highway, can tow a boat, gear and buddy, still get 16+, in 2wd of course. cost 300 in 99 and paid 4 itself 10x already.
gets through nj inspection w/out resetting to original specs.