have a friend in oregon, fabricating twin dump tubes for the 350z TT greddy kit, these dont go back in the exhaust, they get dumped in the atmosphere, easy 30-40hp gain. We made some of these at jotech, costed alot, but it got my buddies Z over 600hp. There pretty cheap, heres the link in case your interested. BTW all the FI 350z owners go on this site, might wana say hello
http://www.my350z.com/forum/showthread.php?t=167335

p.s you might have to join the forum to view pic, if interested tell them Joey Choo referd you. you get a better price.