has anyone found the cause of this issue as I am currently experiencing it? pretty much same setup, gigabit LAN port or computer, cat 6 cables only getting max 110 Mbps, on the laptop with 866mpbs ac adapter getting 220 Mbps?
I was getting 160 Mbps previously through the same LAN port and same cables.
I have tried adding a PCIe Gigabit LAN port and 3 different cat 6 cables to no avail.
virgin media engineer called out and had no solution other than replacing router which did not fix the problem... the reason I pay for the 200mbps connection is for my computer not for any other device.
Problem Solved, looks like it was 'System Mechanic' its auto-optimization of network settings must have been limiting it as you said... I would have thought of this soon but since it's been installed on my computer( as well as the laptop) for over a year now without affecting the speed ( was getting 160Mbps on 150Mbps package) I didn't suspect it.