Just seen these advertised on eBay by bike-enders
http://cgi.ebay.co.uk/DUCATI-S4-MONSTER-POWER-UP-EXHAUST-KIT-888-851_W0QQitemZ8076541317QQcategoryZ10448QQrdZ1QQcmd ZViewItem he's got a low level and high level version of these and reckons they could be adapted for 851/888 use - looks as if they might.
I would only want the spaghettis myself and I'd sell the oval termis on, but I'm £794.50 short of the 'buy it now' price. Might be interesting for someone on here though...
seems a good price since the last set of sil motor spaghettis on eBay went for over a grand