Performance Chip for 99 Cummins

I was wondering if any one saw a difference with a "performance chip" in a 99 3/4 ton cummins 24 valve diesel? I was thinking about getting one but I kinda want to know if anyone knows any improvment..like fuel mileage..i heard you could get better mileage.. but how much? I know you can get a HP and TORQUE increase but what about mileage? If any?

Do not know about a chip, but have you given any thought to something like the Banks six gun. This would allow you to dial in the power level you needed for whatever you may be doing with the truck at any particular time. Such as towing, highway, etc.. I saw Stacy on TRUCKS demo one on a Dodge Dually Diesel, and he actually smoked the rear tires in the performance mode.

no i never really thought about that. Thanks... I will look into it.