[Seattle CTS-V]

I have an appointment this Friday for a hoot, whine problem. Does it nearly all of the time - even while sitting at a stoplight. I assume it's the TSB for the water pump but the car never made that sound until 2 weeks ago when I had the Diff, the clutch, and a Maggie installed. Maybe they broke the new diff while test driving the car for the Maggie install?? Wouldn't that just be great!