Nighthawk X6 R8000 not getting gigabit speeds

Just increased to gigabit wifi and the speed is verified at the modem but speed tests on everything show around 150Mbps.  The router speed test shows 300-400Mbps turned of Qos seting also did a reset of the modem to factory.  New firmware and the trafic meter is off.  I have a cat 6 cable connected and everything is new in the past year.  Netgear support wanted $90 to talk to me and was going to do a hard reset but everything else they said to do I had already tried.  The internet is charter spectrum.  Have done everything I can think of but am getting nowhere near speed I should be.  I have verifid link speed wireless and the speed tests over wifi arent even 1/3 that number.  My network has trafic so after the factory reset I left the default Network name so NOTHING was connected and tried again and still saw around 100Mbps wireless on 1 device capable of 242Mbps and 345Mbps at the router via speed test in router settings.  The bottleneck seems to be between modem and router.  I could use some help.  I realize the wifi trafic slows things down but when I had 200Mbps service I could get 200Mbps at the router now with 940 I only get 345.  I already did everything on every thread I found but am unsure how to roll back firmware.  My next plan is to take the free router from charter and see if it helps.