No!  Let me put it this way, No!   Most of these have been around since the automobile was first invented, but as time goes by they have a new audience.  Just keep your tire pressure at the correct level (psi) and drive easy if you want better MPG.

I just filled up today and I got 27.5 mpg, all city driving for me. 

The tornado: NO

K&N filter: Yes

Cold AIr intake: Yes

Intake will do more then just the filter. Used to be that installing a upgraded ingnition made a huge difference. Now adays the whole system is computer controlled so all you can really do is change the chip or reprogam it.

Ive used K&N drop ins and just took out my TRD drop in. No difference at all in gas mileage. Cold air works if you dont jump on the pedal all the time, my gen1 with an aem cold air was getting like 32mpg. Years ago, more like 15 yrs ago, I used to be a Tornado dealer and yes that really works. Its not significant change, more like 1-3 miles more per gallon. But this is all in refection of how you drive, whatever things you put in, if you jump on the gas pedal all day long, you're not going to get great gas mileage. The tests they do to prove it works, the guy doesnt really drive like we do everyday, he slowly accelerates, he drives like a grandma. So sure it works if you put it that way.

Ive added a Sun hyper voltage system with ground wires, that actually save about 1.7 mpg on my turbo charged Evo 8. On my G35, maybe 1.2 mpg. Im adding one to my new B next week, so I guess we will see.