[Elecraft] [K2] 160m sensitivity below 1.9mc?

[Mike-WE0H]

Is it normal for the sensitivity to drop off starting at 1.9mc on 160 
meters? The power output is 10w across the whole band but tuning from 
2mc on down, there is a real apparent sensitivity degrade starting at 
1.9mc. I have the VCO tuned so it stops receiving at 1.36mc. It tunes 
well above 2.0mc on the other end.

Is there a mod or tweak I can do to keep the hot receive sensitivity 
down to 1.80mc? The BC band is not important but I want all of 160 
meters performing the same.

Many thanks,
Mike
WE0H