[VAL] Aftermarket "chips" for trucks

[Dave Lowrey <airstream@xxxxxxxxxx>]

I keep reading/hearing about aftermarket "computer chips" that can 
improve your horsepower and/or gas millage.

Is this applicable to trucks towing heavy 31' trailers?

I have a 1997 Ford F250 standard duty truck. I would be interested in 
either increasing gas millage or increasing power (but not at the 
expense of gas millage). Are there aftermarket "chips" that do this? We 
have emission testing where I live. They check it via the truck's 
"computer connection" under the dash board. Would this be effected by an 
aftermarket "chip"?

Any recommendations and/or suggestions would be greatly appreciated.

Thanks!

Dave