I suppose the tanks have a vent tube because they did not want to make two different tanks. I do wonder if the California cap is different though, and not vented. None of my other bikes have had gas tank vent hoses. I can see not wanting to trash a $600.00+ silencer! Bike runs great with less back pressure, the FI system seems to compensate fine, no surging, no backfires on over run, adding fuel with the power commander did not do anything that I could tell, although adding 2 degrees of ignition advance at 5000 rpm and up gave a nice boost in power (with no knock). The SMART thing to do would be to fit a quality aftermarket silencer or entire exhaust system. I tried a few Emgo silencers that really hosed up the way the bike ran, no power above 5000 rpm at all, and way too loud. I will buy a new stock silencer if I have to, rather then dealing with junk. The tires did not seem to make any difference in handling that I could tell. The bike still seems very nimble, but lean angle has increased a lot with the fork springs and taller tires. I will not push grip limits on the street, its just not worth it. So I want a longer lasting tire that works well, and the cheap Shinko's fit the bill. They are not hard like tires in the old days, they seem to grip well. On the track, maybe Avon's?