There is a serious issue with Fiat 1.2 engine which I came across few months back. After Fiat has done the free upgrade of car AC, the exhaust of car has started creating a DUB-DUB sort of noise even when the car is in standing position. So how do you verify it - Start the car and drive for few mins with AC on. Stop the car and go back at exhaust. Just sit down and listen to exhaust while engine is on with AC running. I asked about this behavior to Fiat services but they were unable to provide any proper answer. I was communicated by service engineers that this problem has been rectified in 2012 edition of Punto. I have escalated the matter to higher authorities and waiting for a reply. Please note that this problem is not specific to one car. We checked nearly 4 cars with AC upgraded and found the same issue.