Here is the dyno sheet. I personally dyno tested both of the downpipes durring the same session. The dynoing was done on Van Supra's car. The car was totally stock, with a few mods, BIC standard downpipe, no cats, 3" catback, Blitz bov and a K&N filter.
At 10 psi it made 255 rwhp and 267 tq (red rund). After two more pulls to verify the number I swapped the Dp to the DDP ( I have the burn scars on my arm to prove it). The next run with the only change being the ddp the power jumped to 283 rwhp and 285 tq at 11 psi (blue run), thats a 28rwhp and a 18 tq gain. Yes the boost did rise by about 1 psi but only because of the effiency of the downpipe, there was no boost controller or washers used on the car at all. So here you have the facts!!