yeah mak perf was making 860 wheel with the p1x last I checked on an s550 through the A10 auto. Most will never need that much hp, nor have the built engine/trans to support it long term.
You can go with a Turbosmart raceport 50mm valve. Louder than pro-flo but not as bad a red race valve. Thats what I did.
Unsure, probably a bit less than the race red valve.
I cant see where my combo would ever be over 21-22psi so maybe that would be a better way to frame the question lol. It looks like a single big red is good to around 30psi
good thing about automatic trans is that it always shifts before it sounds like a street sweeper
BTW my experience upgrading from pro flow to a 2.0" aftermarket positive seal BOV didn't amount to anything significant virtually 0psi gain and no driveability issues nor improvement.