Not sure about best exhaust. I have an Omrae slip on low mount from a company in Melbourne and it sounds awesome over 6000 rpm. It makes about 95 bhp on the back wheel. As for tyres, as the rear rim is a 5 incher i would stick to a 160 width tyre as the 170 tends to round off too much at the edges. 170/180 width tyres are better suited to 5.5 inch width rims. Go for a soft profile front for grip and not as soft back as there is not as much power as to brake traction lent over anyway.