As I work for Comcast I can tell you how to fix this. You said you have four lines? One going to the bed room, one to the cable modem, one to a cable card and one to a digital box. One splitter is in the wall and there is a three way outside the wall to feed everthing else. What we would do is take the wall plate off, remove the two way and pull the line feeding the bed room and master feed outside the wall. Now take the master feed and plug it into a a new two way, connect the line going to the Cable modem to one port on the two way and jumper the other port going to a new three way, then feed the bed room and the Cable card and the digital box. For the lines going into the wall we would use one of those wall plates that can do cable, phone or cat5. We just wouldn't put the plugin adaptors on. If you do it this way you will not need a booster.