Hey,
This may be some kind of sacrilege part, but when i bought my K1 the previous owner had had some inner bungs custom made to try to quieten it down a bit! They bolt on between the mid-section and the rear cans. They're good quality (i.e. heavy ) and look well made.
I never fitted them myself when i had the exhaust, and forgot to include them when i sold the K1 on a few months ago...
The guy i got them from said they made a difference, but not enough to stop him selling it... so maybe worth a punt for someone?
I'll post a picture when im at home tonight.
All i ask is for a tenner via paypal, to cover P&P which'll probably be around £8 due to the weight.