They don't bring in more air...even if they worked like they said they did.
Thier claim is that it "swirls" the air that
does come in, thus creating more efficent combustion. It's all a marketing ploy. For these things to work, they would have to be in each individual intake port in the heads, and the swirl dams/ quench pads would need to be removed from the heads. Think of all the turns and variations the air has to take past the MAF. First it's "split" by the throttle blade, thend it turns 90 degrees at the plenum. In the lower intake, it flattens out against the bottom of the manifold, then is spilt again 8 times, turns back up into the runners, does a another U-turn near the top side of the runners, then down into the intake ports, which curve, past the valve, which "spreads it out", hits the swirl dam/ quench pad in the combustion chamber of the heads...where it is FINALLY mixed with fuel spray from the injectors.
If this thing can keep the air swirling, "promoting better combustion and adding 20 HP", after all that, I want MT to start carrying them...I'll buy 2.
I have an electric hair dryer that I'm gonna fab into my intake system...it has a high and low setting, so I can change the amount of boost. I'm gonna hook a shop vac up to my tailpipes as well...to "promote better exhaust scavenging"