I have an Archer T9E | AC1900 PCI and always worked perfectly. Lately he has been very slow. The "Tx rate" stands at 13 mbps on a 5GHZ connection that always worked close to 1300 Mbps. My system is 10.13.6. Do I need some kext? It was never accurate.
Following the installation of the link: https://www.tonymacx86.com/threads/unibeast-install-macos-sierra-on-any-supported-intel-based-pc.200564/ and using an attached EFI folder (i deleted the SMBIOS information), I was able to leave running 100%. Video card, audio and all USB 3.0s running well...