Performance Chip- Power and Fuel Economy

I ran across someone on eBay that custom programs chips for OBDI GM vehicles and he said I can get an increase 6-7 mpg, 25-30 HP and 30-40 torque with his chip. The chip is only $105 delivered and a money back guarantee. What do you all think? I currently have a 1990 Chevy Sub. and get around 16 after a tune-up so +7 mpg would be awesome.

http://cgi.ebay.com/ebaymotors/Chevy-5-0-5-7-TBI-TPI-305-350-suv-van-truck_W0QQcmdZViewItemQQcategoryZ33597QQihZ005QQit emZ150148509648QQtcZphoto

Not sure if I would believe a performance chip would be able to give you a 35% increase in MPG.

Hard to believe that GM engineers would not want to sell that to the public.

Just my opinion.

Sandman

I presume there's a money-back guarantee.

You've already covered all the factory bases, 16 mpg highway is near the top for a small-block '90. For only $105, why don't you try the chip? If you get positive results (even 2 mpg would be worth it) let all of us know!