Hello, new to this and to asking for advice via forum, any help or direction would be appreciated,  so..... just brought a 2007 VRS TDI on 119k, driven approx 300 miles now and  noticed a slight popping/thud noise when revs drop to idle, nothing noticeable in physical feeling or performance but as anyone who buys a car and notices something it makes you wonder or over worry ?? I’ve got 6months mech warranty and would like any feedback so I can go back to the dealer sooner than later as I stand more chance of them rectifying any issue, thanks in advance and if more detail is required I’ll update, thanks 

Has it been modified?

@xman No not modified or at least that I am aware of, Drove to work this morning and seemed as if it ""could"" be exhaust knocking very gently but I have looked underneath and cannot see any signs of this however really need to get it on a set of ramps to examine properly,