I experienced the same issue with Fa 77 and my new K-5. After "wow" effect faded a bit, I found that it has severe backfocus with that lens. At first I tried a very contrast target - a white box with black printing on it and performed tests from 1-1.5m distance. Testing showed that even +10 is not enough
I entered into debug-mode through PK_tether and dialed AF to +110. Now 1-1.5 m subject was in focus but when I tried to take pictures of some real objects I found that at 2-3m distance I got front-focus. I was pretty upset and decided to wait for good lighting conditions. Next day I was lucky with sunny morning, I first tried real-life subjects (my wife and cat
) at 2-3m distance and then re-tested on 1-1.5m distance. Now AF in debug mode was set to +70 and AF fine adjustment set to 0. Both, distant subjects and close-ups were perfectly in focus even with low ambient light conditions and tungsten lamp.