Are there any gas saving gadget that really works? What about the turbonator?

No. According to that myth show on the Discovery Channel (I forget what it is called) there’s not.

Just earlier this week they did a whole episode on this very subject. They tried all the gimmicks you hear about and not a one of them worked.

So, save your money.

No not really.

A product called Gumout will work. If you get the entire package instead of just the liquid poured into the gas tank it will make a difference.

waiste of cash

Turbonator is a scam.
Very moderate increases can be had by cleaning your fuel system.
Also a slight increase will follow getting a better air filter, maybe even a CAI, but not enough to justify the expense.

A more effective method is to spend no money and just make a few little changes:
Drive the speed limit, or a bit less if the limit is over 45mph. Unload any excess junk from your car. Keep your tires inflated properly. Dont accelarate too quickly.