I saw something on Iroz Motorsports in the US saying that the second rattle you're referring to is actually the turbo wastegate and not a rattle of some kind in the exhaust from the valves or anything else like we all thought even though it sounds like it and the only way to solve the issue is by upgrading the turbo and in turn, the wastegate.
According to Iroz you can try a little trick to be sure that it is the wastegate which requires a cheap hand vacuum pump and force the wastegate closed at idle and 'blip' the throttle and the rattle shouldn't be present. I'm not sure how or where you'd attach the pump but its worth a shot for the technical guys out there and give us a solution in terms of a fix