Nothing happened to the stock block, just got the shortblock for piece of mind, and because I'm shooting for 600whp. As for the cutouts, they are working great for me, mo leaks whatsoever. When tested on the dyno, they made a small amount of extra power (5-10whp). I do feel that the car is more responsive with the cutout closed when pulling through gears, though.
I do love having them, though. They sound fantastic (extremely loud) and coupled with the turbos, it's really unique. I love stopping at a light and herring the turbos spool down
It's a great option for me, because I rarely like making that much noise, though.