Downpipe Difference?
 

DOes anyone know if there are really any advantages to these dual pipe downpipes and "Power pipes" that companies like ReAmemiya and Knightsports are selling. I mean they look to be bigger diameter right at the start of the pipe.

i haven't seen these yet...links? pics?

http://www2.ocn.ne.jp/%7Eknight78/fd3s/fddft.jpg

Supposedly, keeping the exhaust separate until later in the exhaust line helps improve torque. I've seen a lot of FC race cars do that. However, I'm not sure of the effect it would have on the FD. A local friend had a divider welded into his downpipe but I don't know if he ever did any before/after tests.

Dual pipe downpipes.
Derived partly from the drift scene, partly scene street.

On some cars...the lowest part of the car...was the exhaust piping.
So in an effort to reduce the chance of scraping things like your downpipe (or in some cases...ensuring you actually have an exhaust)...they use 2 smaller diameter pipes to replace the 1 big diameter pipe.