2005 boxster s - buzzing sound at 3k?

[smc]

Just returned my 1 month old Boxster S to the dealership to get them to look at this. In my case the noise occurs at 2200rpm, only when the temperature gauge passes 60 and up to 5 mins after reaching normal operating temperature of 80.
The story from the dealership is that it is a design feature. They explain that it's an air pump that injects air into the exhaust system to meet US air quality regs. Sounds like an engineering kludge to me but no fix.