I have just had a quick flick through the instruction manual and I can't see any settings you can change that would remedy your problem. It sounds like you are getting a tonne of packet loss and that may be a result of loss of data as it goes through the power lines in your house. I am assuming the "full bars" are on your laptop or wireless device you are using to connect to the adapters. The best thing you can do atm is if you are using a laptop try and ping the router and see if you are getting any packet loss on your connection to the router. To do this, open a command prompt (click on start, click run (OS depending) and type "cmd" in the search bar and it will open up a new window).
You will need to know the ip address of your router. If you have got a shub in router mode it will be 192.168.0.1 and if it is modem mode, or if you have a 3rd party router, it will be 192.168.100.1. At the command prompt type "ping 192.168.100.1 -n 10 (or replace with the ip address of your router).
Hit enter and you'll get something which looks like this:
If you get any timeouts on any lines as it runs the test and it comes back at the end saying 50% loss (example) then that means you are losing packets between your laptop and the router before anything even gets out of your house.