HPP in on the money. I've seen multiple cars put out great numbers on safe tunes. Manny knows what he's doing. He got my 98 cam/bolt on gt to put out 320hp/340tq.
Hpp's twin kit is definately worth the extra money hands down. You will not be disappointed with it. Manny is really on top of things especially tuning.
HPP Racing (Manny I believe is his name) makes a killer kit. Best option if you got the coin. The only thing I'm not wild about their kit is the piping isn't SS. But the lifetime warranty it (which I believe is still in place) kinda makes up for it.