Well, with that 5hp gain compared to other exhausts, it is relatively the same or maybe more horsies. The convenience of quiet stock exhaust to the "10db" exhaust open header seems pretty powerful to me.
As some more researching on PreludePower.com, the low RPM will probably lose power due to my mugen header to straight to open header, and my high RPM (vtec and higher) will probably have good gains. What I said there is myth of back-pressure, and from logical point of view, it sounds very true.
But if you're considering racing in a line, getting up to high RPMs do not take too long especially in first and second gear. Hopefully I can get this soon and get my little girl dyno'd and show you guys some results.
I plan to have "interchangeable" CAT/ECS, it is kind of hard to explain, but I will try to anyways. Since I do not know if the backpressure myth is true on our cars, I will try to have the CAT and the ECS/YPIPE interchangeable, for example, I can do this:
1. mugen header -> ECS/Ypipe -> CAT
or
2. mugen header -> CAT -> ECS/Ypipe
This will allow me to try out the back pressure theory. Hopefully I can use this interchangeable idea to replace the ECS/Ypipe with the stock piping to fool emissions, etc.
This reminds me, I bought a "Carb legal" plate from a DC sports header to put on my Mugen
Let me know what you guys think of my plans, this will be my next mod (hopefully).