Engine Rattling And Whining Sounds problems of the 2010 Cadillac CTS

Cadillac sent me a letter dated June 2014 with my vehicle's VIN on it indicating that "the supercharger may develop a noticeable rattle noise at idle. The noise will typically go away when the engine rpm is raised slightly above idle. However, if left uncorrected, the problem, over time, may lead to contamination of the lubricating grease and cause the bearing to squeal. If left unaddressed, the bearing may overheat and can cause the engine seizure or no-start condition. " Cadillac then goes on to say that they will extend the warranty for this issue for 10 years from the service date. I brought my car in to ed morse Cadillac in sunrise FL in Jan 2015 with this letter because the car had the noise as described in the Cadillac letter. The service adviser advised that this car was not one of the vins covered. ??? I just brought my car in for an oil change and the three mechanics all heard the noise and indicated it sounded like something was wrong. I called up the Cadillac number 1-800-204-0261 and basically "min" told me that this isn't a recall but an extension of the warranty, so despite Cadillac sending me a letter indicating my car may have this specific problem that they will fix and that my car has the indicated symptoms in their letter, min at Cadillac says that I would have to pay for the diagnostic costs for Cadillac to determine if the problem as indicated in their letter is indeed what they sent me the letter for. I find this unbelievable that Cadillac is putting the onus on the customers to risk the cost of teardown or a major engine malfunction and accident, instead of recalling these cars and taking care of the problem that they notified me of. Why should I be fronting money to diagnose the problem Cadillac says I have??? clearly Cadillac would prefer the warranty to run out and not have to pay for $3k repairs on all of these cars.