Will installing a fuel saver affect my vehicle Warranty?

A. No.
It is an after-market product.
By law, in North America, vehicle and engine manufacturers cannot void a warranty if the customer adds any after-market product.  (I’m not conversant with other countries policies)
A specific USA Law is the Magnuson-Moss Consumer Product Warranty Act of 1992 that states manufacturers may not void a warranty if after-market product(s) are used or added unless that equipment manufacturer can demonstrate that the product(s) caused harm to the engine.
Further, if there is a warranty claim, and the manufacturer wishes to ‘blame’ the after-market product, the onus and cost is on the manufacturer to prove how the product caused the issue in question.  With our technologies I’d certainly qualify as an expert witness to dispute any claims they make.
Even if they can prove an after-market device caused a problem, they still cannot void their warranty.
The Vehicle Manufacturers (quite rightly) just don’t have to pay for specific damage caused by some other product.
We’ve designed our Fuel Saver Technologies to safely and smoothly interact with all vehicle fuel, electrical and electronic systems.  They do not modify the original specifications of your vehicle and are designed to enhance the combustion of any engine.
Aside from improper installation we calculate there is zero risk of damage to the vehicle or engine.
Here is a link fully explaining the Magnuson-Moss Warranty Act: http://www.mustangforums.com/m_1524512/tm.htm