Ok, Tony, I see where you're saying there could be a pulse during the overlap from exhaust to intake. I don't see that happening however because the piston dropping as the intake opens would neutralize any pressure difference before pulling from the intake and closing the exhaust. I'd really rather not start a huge debate on this subject, but as I've said before Tony is extremely intelligent in these areas. On this particular point though I think I'd have to disagree. An exhaust gets a huge burst of pressure being released where as an intake is a smooth flow drawing in and a slight push out. The pressure in the intake neutralizes before changing direction therefore stopping any sort of pulse from being created. Anti-reversion efforts are used in intakes to help balance the tranistions from cylinder to cylinder and keep from creating a huge positive pressure pocket within the intake that could cause things like pre-fire which can seriously damage seals, sensors, injectors, jets, valves, etc... When you start doing some serious fine tuning for things like that you're looking at a high race engine with a heavy cam and lots of overlap. Anyhow, I digress. Again, I need a white board.