I remember FT86speedfactory has been developing a center exhaust for a while that replaces the 3rd brake light. It's in the velox rear diffuser thread here:
http://www.ft86club.com/forums/showthread.php?t=87941
No idea when it'll be released though but it looks pretty cool. Better than the single circular exhaust hole above. I also remember seeing a pic a while back with a custom made 3 hole center exhuast like a corvette! lol Here's a dual center exhaust one that I just found:
http://www.frs-tuner.com/noblesse-st...os-and-review/