I may add, do your research on quality etc, as you obviously are.
You get what you pay for these days. Cheaper systems may bite you on the arse. Not an issue for me as can do my own repairs etc.
those wondering, the ML and MN run same system other than the dump, Be very easy for any company to make the dump suit the MN from their ML systems.
3" is overkill unless chasing huge numbers and need to get rid of the heat.
I actually think the factory system is well up to spec on stock to mild tunes. The factory dump is quite good on the MN.
Also, keep in mind, with the variable geometry turbo you cant actually pick up the flange with 3". 2&3/4 is plenty.
I was doing some work on the pressure drops with the MN's system. (Have run out of time) looks like with milder tuning the 2&3/4 back to 2&1/2 behind dump then back to 2&1/4 for tail retains good flow and scavenges best with out big pressure losses.
On wilder tunes we need the bigger system to get rid of the heat.
Got me buggered why they dont make them 3" and drop back to at least 2&3/4 for the tail section. Be cheaper, quieter, easier to fit larger spare, and theoretically give a tad more off boost torque.
When hot air cools it becomes much denser. cools around 200c every 6"'. (this is why we use intercoolers on the pressure side of the forced induction)
With oversized exhaust, the gas cools, becomes much denser, losses velocity, falls into a void them actually can become more restrictive as wont scavenge.