any one have these http://www.mccordcg.com/mpp/mpp.htm
how do they seal and dose it make it sound like you have a header leak when there shut

Not this specific product but I have run cutouts on a street/strip vehicle I used to run. It worked fairly well but I did have to keep some extra gaskets around. On and off enough and they didn't seal right after awhile. This version "may" tend to reseat the seal in the same alignment better than doing it by hand and therefor, "may" live longer. Nut again, I don't have specific experience.

-Blair