The power differences are not going to be that drastic. The difference between the two systems are going to resemble the same power differences between two Evos. If your really interested in power gains; then it's going come from fuel tuning that exploits the flow capabilites a 3 inch exhaust. Look for the one with minimal bends (mandrel of course) and carries the same diameter through out (doesn't neck down at the cat).
I have a B.R. downpipe, but it's the 2.5in. It looks like it has the same slip fit to the O2 housing and it was a real bitch to install. It's accually coming off tomorrow in favor of a 3 inch downpipe that utilizes the stock doughnut and springed bolts. I also have just a Magnaflow muffler, which has a good tone, but it's a little loud.
I have a B.R. downpipe, but it's the 2.5in. It looks like it has the same slip fit to the O2 housing and it was a real bitch to install. It's accually coming off tomorrow in favor of a 3 inch downpipe that utilizes the stock doughnut and springed bolts. I also have just a Magnaflow muffler, which has a good tone, but it's a little loud.