That manifold has been out for a while now and I have yet to find anyone that has done back to back test against the stock pi intake. One guy that tested it upped the boost on his turbos at the same time so there is no way of telling what the increase was from the intake alone.
My only concern with it is that the intake runners are slightly shorter then the stock pi intake wich would most likely hurt low end power production. I however am not a expert and dont know how it was designed so it may even pick up a little power in the low end. If you are seriously looking into a new intake I would either go with a trick flow or the hps. I think that most can agree that the typhoon is a piece of junk and the P-51 is just flat out too expensive so that leaves you with those two choices from the aftermarket.