I recently bought a 1999, 911 C4, with 36K miles on it. It passed through service with no issues - I had all services updated out to 90K to 'reset the bar'. The does, however, make a 'pop' sound that is audible in the roof when the body torques, i.e. pulling into/out of a driveway at an angle. Is this a common thing or to be a concern? I would appreciate any insights - thanks.