Jon,
I take back what I said about your bike - it's disgusting! When was the last time you cleaned the underside of your tank?!
Someone will be along soon who knows what they are talking about so I won't even bother attempting #1.
For #2, don't scrimp on tyres if you have a sportsbike- they're the things that'll stop you sliding down the road! I use Diablo Corsas which I have been very pleased with - warm up quickly, sticky and great feel. I've never tried Diablo streets so I have no comparison. Having said that, for only 50 bucks more you owe it to yourself to give them a go.
Although you say you use it a lot for commuting, this must be a short journey if you are only filling up once a week! At around 100 miles a week you can get away with one set a year (although you could shred them in a day on the track
). Let's face it, if you wanted a cheap, reliable, average handling bike you'd be on a MZ, not a duke!
cheers, Chi
[Edited on 12-11-2004 by chicken]