you could also try some paint renovator I used the autoglym stuff on mine - try a small area first though ;)
http://www.autoglym-online.co.uk/product/autoglym-paint-renovator/
I would certainly be interested in your review - nice one.
This type of cleaning product may help you with the brake dust spots
http://www.angelwax.co.uk/?wpsc-product=revelation-fallout-remover
Yup you will get a slight increase in burble but as Gambit says to go further you will need to look at the system as well - the Prodrive on the back of mine gave a great sound without being too intrusive