I see lots of inexpensive "miracle products" listed on E-Bay that promise to add up to 25-50 horsepower and 35+ ft/lbs of torque, and an increase in fuel mileage by 25% or more. All for the low cost of $20!

Has anyone tried any of these products? Is their any truth to their claims? Do they work for more than a couple of months?

Thanks for the replies!