Slow Ethernet, fast WiFi

@manuelrios509 I will watch this post. I have not experienced this type of issue. 

Generally, if you speeds drop when adding a router, the the router would be suspect. But, if you get the same results with different routers, then the problem is difficult to identify. 

It is not my experience that TM throttles speeds. Instead, because we are on cellular networks, the traffic is prioritized, and home internet takes 2nd place over cellular phone traffic. That's why some parts of the day (usually evenings) speeds are much faster than morning and mid-day (commute traffic).

Have you tried setting your router us as an AP, subordinate to the TM gateway? Can you describe your setup? Have you considered taking your gateway back to the local TM store, explaining your issue, then asking for an exchange unit, and ask for the Sagemcom unit? I have the Sagemcom 5688 Fast gateway with Netgear MR60 mesh wifi router and it works consistently well.   

I hope this helps!