How is the C2V 'reflector' mounted? It should not be in front of the DB4e.
I have seen enough reports of TiVo's having this type of difficulty that I'm fairly convinced the OTA tuner used in the TiVo may be a problem... However, don't give up. I would keep trying alternate mounting locations and elevations.
While seeking a location with acceptable signal conditions, use just the antenna assembly, one coax, no splitters or amplifiers and only one connected tuner. (The TiVo is the most critical but consider switching between the TiVo and a traditional TV with ATSC tuner.)
http://forum.tvfool.com/showthread.php?t=13646