Here's a great vid explaining VVT, and how it switches from "non overlap" cam timing to overlap cam timing, and demonstrates exhaust scavenging with some reversion into the intake. On a normally aspirated car this would have the benefit of bringing in more air, however on a f/i car this would only work to slow down the intake charge (almost like reducing boost would).
http://www.youtube.com/watch?v=9A6S1NUjg_A
