Slow speed via MR60 (wired or wireless)

I have a Set of MR60 ( main + Satelite)

When I am connected to My ISP modem directly  ( Cable Technicolor Modem ) I get full internet spead +120Mbps

When I am connected wether its wired or wireless .. I get on average 2 to 3 Mbps download ( ridiculous ) 

I was on firmware version 1.0.6.102 

I was asked by Support to manual upgrade to 1.0.2.112

I have rebooted the device and i  have also reset it using the pin ( Firnware remain updated ) 

I  have done the proper power cycling of both the Modem and Router as well has my laptop ( flushing the DNS etc... )

They made some changes to my Channel ( 2.4 "9" ) and (5Ghz "161) .. they also changed mu MTU from 1500 to 1492

Then save the changes and said to monitor for 24-48 hours if still slow to call them back. 

Eberything was perfect yesterday, not sure what could cause my devices to just stop delivering the full speed?

Any help would be appreciated.

Thanks