DirtRacer , I use a 5 port with the standard Hyper 8 Pro exhaust and its got major balls, slight sleeve work and get 10:30 mins out of a 125 CC tank, comes out of corners like a bat outa hell, dunno about the Hong Nor pipe tho, havnt tried it cause ive been very happy with that exhaust ive been running, Mark from Massive Mods told me about a LRP exhaust for the 5 port, cant remember the part number but he reckons its extremely good with the 5 port and hurry up and sell me your OS motor :]

Pretty sure this Pipe with the Go Tech 5 port - http://www.lrp-electronic.de/e/lis/0...d-Exhaust-.jpg