I have minimal to next to no nvh in high load low rpm situations but I run stock bushes, stock mounts and factory oil with a full titanium akrapovic exhaust, akra in their infinite wisdom put flex joints in their dp but they are tiny compared to AR design
Even though they are near a perfect fit still need some kind of flex joint to relive fitment situations.
When I ran the stock mids they where horrible and definitely need some kind of flex joint.
GGMR2T try the flex joint on both your mids and you will be pleasantly surprised how much better the fitment gets and lowers the nvh.
Not saying it will get rid of all as there is to many variables in most peoples setups but it did in mine and will definitely help a lot in most.