My 07 Cayman has developed an engine whine that I can't solve. It seems to be more evident from 1500-3000 rpm, above that it's drowned out by the exhaust. It is rpm dependent, does it in gear and neutral, warm or cold, ac on or off. It always seems to be there in those rpm. Mentioned to the indy in the last service, they changed a pulley but whine is still there. No coolant leaks, no change in performance. Any ideas?