[Elecraft] K2/100 output variation

[G3SJJ]

I am sure I have seen a discussion about this one before. During an 
enjoyable 160m opening to the Right Coast just before Christmas I was 
running a few Stateside stations and noticed a definite output power 
variation coming from my Acom 1000 which was being driven by the K2. I 
would guess that the drive power was varying between 30 and 50 watts. 
Any thoughts on this?

K2/100 5545 bought at Dayton this year, completed in September.

Chris G3SJJ