Did you try to do some testing with Signal Quality,betwen BCM 4501 AND BCM 4505(plug tuner)
I hawe dm 500 hd(bcm 4505) and signal quality is beter then DM 8000(bcm 4501).I se that on the low signal quality transponders(11095 16E),there i cuold watch until 24% of signal and on the dm 8000(bcm 4501)i could watch until 29%.Also when the signal is good he goes(on the dm 500hd bcm4505) up to 48%,on dm 8000(bcm 4501) he goes up to 39%.