Dual Monitors Dim

I have a customer who moved to the area and brought his truck to us.  He has a mid-grade video booster that sends signal to 2 Pyle LCDs in the headrests.  Whenever a scene comes on with bright light or lots of action, the monitors dim.  I believe it points to the booster, but I wanted to get more input, possibly a place he can look online to buy a high quality booster that will provide enough power for both monitors.  Thanks for the help.

What brand of video amps does he have? I know that has affected some of the quality of our tv's. We have always had great luck with Farenheit's video amplifiers, and have had many problems with Pyles. I would also check his grounds and power source as well.