Flex pipe problem/vibration/rattle

[DreF79]

Hi guys, I'm very new to this but hoping you can help. 

I'm getting a distinct vibration in the cabin and a low rattle sound from my 2015 B8.5 S5 in the 1k and 1200 rpm range (both acceleration and deceleration).

From what I can tell, it's a common flex pipe issue that can be fixed by either replacing the downpipes entirely or simply replacing the flexpipe section by cutting out the old and welding in the new part. 

What I can't seem to find out is the details or exact specifications for the left/right flexpipe sections. 

Has anyone had this issue before and can give me some advice? 

Many thanks!