I know Jeff Taylor had it on his Hytech unit, but what is the HP factors behind all of it..........

thanks in advanced.....

 

ttt

 

I believe it has something to do with equalizing the flow of the exhaust gasses along the inner and outer (far) walls of the header, as well as allowing the exhaust gas to follow the inner bend right off the head better.

 

http://www.team-integra.net/sections...sp?ArticleID=4

This url goes very in depth about D shaped ports