I have a K&N cold air induction on my Nissan Titan. The performance is a lot better and I get 2MPG better than stock. Considering the gas mileage I get that is a huge improvement say 17%. It has paid for itself in the first six months, and will save you a lot of money in the long run. DO NOT buy anything that promises huge gas and horse power improvements because it is more than likely b.s. IMO K&N is better than all the others simply because you know what you will get. If you decide to go with a cold air kit, be very sure the intake is not going to be in a place where you have to worry about water, mud or anything else you can imagine getting sucked in the engine. Mine sits up high on an already tall truck so I'm not worried. Another good investment for saving gas mileage is a superchip (depending on what type of vehicle). You can program your car's computer to get better gas mileage and performance. The only problem is you have to run premium on most vehicles after installing the chip, but I have read reports of many people improving their gas mileage by 25-35% depending on the vehicle. I know on the 00-05 Chevy trucks with a chip and intake you can get 26 MPG highway with a V-8 on a pick-up!
As far as the Tornado intake goes it is an expensive piece of ____!