I have been having REALLY bad pixelation on JUST the High Def Channels ever since I installed the Tivo HD XL which I bought in December of 2008. Thanks to this thread and a particular poster, I have it licked (almost) I got that atennuator pack today and just finished with them. I ended up with a total of 16 DB attenuation. 13 with a 10DB and a 3DB attenuator connected to a 3.5 DB splitter. I have not checked all of the HD channels but the ones that I had found and marked on my program guide printout are working perfectly now. The one exception is 583 (Speedhd). It had the worst pixelation and still pixelates albeit not as badly. I also found that the pixelation problem IS tuner dependent. Ie. SpeedHD is MUCH worse on Tuner 0 than on Tuner 1.