I've heard of straight through exhausts breathing better and let the bike run lean.
I've not been real hip on why, I can understand if you change the way the air enters, but get fuzzy on why once past the exhaust valves.
06 Paul Smart Sport Classic NFS ever.
08 S4RS Tricolore #081 NFS ever.
01 M600, aka, The Pink Monster
97 900SS CR
72 Norton Commando 750
03 KX60 with S4R rear shock,Honda CB350F, Hodaka Ace90, 3x Yam-YGS1, Yam-CS3 200, Vespa small frame, Gilera 106, Puch Sabre, Puch 50 Boy Racer, Ducati 250 bevel, Benelli 250, Benelli 360, Honda CB350T, and many more.