I used JB weld.
No, really, I did, because some of the "HKS" flanges that are floating around out there are not machined properly. If you mount the SSQV on them, with the o-ring, and the snap ring fully seated you can still blow air around the seal. I used the o-ring and some JB quick (inbetween) and the snap ring to put mine on my EVO. I pressure tested it after about 50 miles, no leaks.