Gigabit not really gigabit

Hello,

I am only getting about 150mbps download with gigabit service. Xfinity test results are much higher than reality. My IT Department knows this based on the performance issues of some of my applications. It shows 500+ mbps but experiencing latency issues. The gateway wifi is not good for my 2 story house and basement office so I purchased an Asus RT-AC86U and running the gateway in Bridge mode. I am still getting 150mbps. I can see on the Asus interface the speeds and they are not even close to gigabit. I have no other companies in my area. Any suggestions?