I have a Dell Inspiron 13 7000 (7359) 2-in-1. The MB was replaced.
Now when I use the Dell support site to scan my system the
Tag and description says Dell Inspiron 15 7000 (7568).
The Intel Dual Band Wireless-AC 3165 is installed and using the latest Intel Drivers by using the Intel driver check utility.
The Dell Inspiron when connected to the 5Ghz wireless, never exceeds ~79 Mbps. .
The router is the latest Xfinity "b" router. My Thinkpad with 5Ghz is getting 130-170 Mbps.
So I don't believe this is the Router.
Also when I connect the Inspiron with the Dell RJ45 to USB connector, the speed never exceeds ~80 Mbps.
So this seems to be related to the laptop.
I checked all the wifi power settings and read the support notes for Adapter settings.
Nothing seems to improve the speeds.
I was able to resolve the problem. The issue was the WIN program Smartbytes.
I recommend everyone remove this from their computers.
Right-click on Windows Icon
Select Apps and Features
scroll to the program Smartbytes and remove any software associated with Smartbytes.
My peak speeds went from 70Mpbs to 200Mpbs.
I was very glad it was nothing to do with the motherboard. It was the fact that
the Smartbytes software was activated/installed when the board was installed.