I want to use a set of longtubes, and I am wondering if the o2 bungs must be installed on the headers or the H-pipe. Also I was wanting to make my own H-pipe but I wasn't sure whether the pipes must have a crossover pipe connecting the longtubes, or can I keep the exhaust pipes seperate from each other and route them out the sides? Does the crossover tube on a real h-pipe add HP or torque, is that why they do it. I know this is probably a dumb question cause I have seen lots of cars with seperated exhaust, but I am looking for the best power on this EFI application, and I know they like scavenging. Thanks for the help