There is a very cheap mod described and discussed on the Ducati.ms forum here:
Gettin' More Sound Out Of the Stock GT1000's Pipes. - Ducati.ms - The Ultimate Ducati Forum
Basically, it involves drilling two holes in the end of each can to give the gases an easier and shorter route to the open air. I've done the mod, and it certainly improves the sound at idle, but I haven't been able to test it on the road yet - too much bl**dy work!
According to the posters on the forum (and the thread is huuuuge), it improves the sound of the bike, and also - according to some - liberates a few extra horses and smooths out the low-speed vibes. Worth a look.
Anyone else seen this and done the mod?