They are rediculously easy to make and simple to install.
It seems to depend on which article you read or who you ask as to whether they actually improve fuel mileage or not and whether or not while using them you need to adjust the fuel intake thus possibly causing damage to the engine.
I can tell you that I can buy a bottle of 101 octane booster at the Dollar Tree for a buck and improve my mpg by an average of 4.
Anyway, I can't wait to read your opinions on them as I personally know of noone who is currently or has ever used one.
Thank you in advance.
Jack the curious.