Doesn't the race header screw up your emissions compliance?
Here's what Comptech emailed me:
On the 06 Civic SI we did four tests; 1)stock exhaust/stock header, 2)our exhaust/stock header, 3)stock exhaust/our header, 4)our exhaust/our header. The results of 2 and 3 where pretty much the same, yielding about 1-2 hp. When combining both aftermarket header and exhaust in test 4 we realized about 7hp. So on that car you really need to get both, not just one or the other. If you are going to keep the car N/A long tube headers will be your best bet for more hp. If you are going to supercharger the car you will probably see similar gains with either header. I’m sure the long tube would still win out slightly in the top end. Once again though, most of the long tube, eliminate the cat, headers are gong to be illegal for street use in California and other various states. If you live somewhere where there are no emission laws then go for it and do what you want.
My current thinking is to do this plus the Injen intake and the Hondata reflash. I'm not interested in seriously stressing the engine, going FI, or doing anything radical. A nice, smooth HP bump, lower VTEC point, and higher redline should suffice.
S.