Yes Really...I am not expert in editing SSDT or finding issues with Kexts but my System runs fine with 1503, with 1704 USB 2.0 and all USB 3.0 Ports onboard are gone, only the Three Ports most right at the Backpanel working.
Back again with now working USB on my 1704ed X299-Deluxe...had to push Boot-flag npci=0x2000 after that it works.
Had Battery removed, Powered off for 10-20 Minutes und CMOS resetted it about 10 Times. Changed nothing, only npci=0x2000 like @kgp told, did the Push.
Now on 1704, new flag in config.plist--we´ll see.
Hmm ok, got 2 Vegas in my Rig, maybe it will not boot with 4G Decoding set to on, will try...