Hi, I bought a 1983 Heritage special around the 1st. of june and have been tinkering with it as time allows on the farm. My plans are to do a street tracker type build this winter. The bike was missing one air cleaner and had leaking carbs so I put on a Joe-Wiseguy two into one tracker intake and jetted up a 36mm Mikuni VM I had for a TT500 Yam[special thanks to Tee-Cat on this site for answering my e-mails about his set-up] and the bike really runs great with the single Mikuni. Starts first kick, idles smooth and pulls strong. I saw on the Australia XS650 site there was mention of a company in Minn. called Thunderproducts that sells a tuning piece for the Vm's called Ultimate Port Optimizer, appears to be a plastic piece that you attach to the bottom of the slide and it fills the slide cavity to cut out rolling air turbulance to give better fuel atomization. Claim three/forths to 1 h.p. gain per 100cc of engine disp. Wondering if any one here running VM's had any experiance with this product on their 650's? It's Thunderproducts.com if any one is interested. Mitch