That is my understanding of it.

 

What you are referring to exhaust gas reversion. I doubt that it is a problem with a s/c as there is more pressure and volume coming in than out of the engine from what we see on the gauge. What happens with vacuum , I don't know, but with a pd blower it shouldn't matter.

Post #2 here seems reasonable: http://www.speedwake.com/forums/showthread.php?t=36833

I know, it's old and from a boat forum, lol, but just replace carb with throttle body and water (reversion) with exhaust gas reversion and it works.