I've had these devices for a few years,  but recently upgraded broadband to 990mb, did a Internet speed test on each of my devices  (i have 4 of them, with router connected to 1 down stairs), from different points in the house (down stairs & upstairs),  and have abysmal up down speeds!?

The devices have the latest firmware through the tool. 

I have tested over WiFi direct to router and this gets 150mb (twice that of powerline).

Direct wired eth connection gets 990mb from router.