The standard spring in the type S is rated to 25 psi according to greddy, they also have a 30, 35, and I believe a 40 psi spring upgrade for it, although, I think for anyone running that much boost, that valve is just simply too small to release enough pressure...

But keep in mind Jeff, these DSMers you are talkin about running 26psi on these, are probably also only using a 16g or something comparable...