Nichols Manufacturing in Milpitas. They work only on Ducati's and they have a great reputation for the quality of work they perform as well as their integrity. Ask the same question in the Ducati Index and you'll get the same endorsement. All the service on my '01 996S has been performed by them. John, the owner and Jim, the shop manager are awesome. Call them at 408-945-0911.
They actually work on all sorts of bikes, but Ducatis are definitely their specialty. Let's put it this way.... How many Ducati dealers do you know of have the expertise and equipment to not only service motorcycles, but the Aerospace industry? Ducati North America couldn't troubleshoot their way out of a paper bag, part of the reason why so many in this country opt (settle) for Japanese. Expect to pay about half what DNA would charge you for a valve job (and it will be done right the first time).
By the way, while they're working on your bike, about a half-mile north up Milpitas Blvd on your right (corner of Dixon Landing), there's an awesome Fish & Chips mom & pop operation called Half Penny Fish & Grill. Mmmmm.... Okay, yep... I'm going there tomorrow.