http://www.flymagazine.net/archive_bands_article.cfm?id=fa67026aSo according to Mike, he, Bruce, and Al never did anything more than pot, if that.
Mike always gives pretty funny interviews -- I like his reasoning for Brian not being in the band: "See, Brian and his people, the people around him, are focused on Brian Wilson the soloist. I guess they want to make him Billy Joel or something, or an Elton John, a piano man."