from what i understand with vacuum you could estimating increase hp 10-20, it also helps the
oil drop out of the crankcase because the vacuum doesn't hold liquid as well.
the regulator does have a filter. you can also experiment with putting a hole in the blowoff valve piece below the spring. if that doesn't work then put a piece of aluminum between the spring and valve to block it and put a regulator in. if you are pulling 2-3" at idle which is what mine does, you will need something. the 2 scavenge stages are probably enough, they just have to be in the right places. sounds like you have a good handle on it.