Here's a nice review of the Berk's:
http://www.3 7 0 z.com/MagazineArticles/tabid/57/ArticleType/ArticleView/ArticleID/43/Default.aspx
(get rid of spaces)
Dyno is on page 5. The results seem a bit...ambitious, but nonetheless gains are MUCH more that 3 or 4hp. I think it was test pipes that showed minimal gains over HFC's. I believe FI had a video of their dyno sessions a while back to compare stock, HFC and test pipes.