Ford Focus 2.0 Duratec-Rear o2 sensor blip

Would the drop in the rear o2 sensor confirm a sticky valve? I have a tick and the vacuum gauge has 1'' of flutter. It happens at idle and low rpm sometimes.

I went back and looked at your other post just to see if there was any more to this. scannerdanner.com/forum/post-your-repair...c-2-0-high-ltft.html
I would definitely want more than that to hang my hat on before calling a valve train related issue.
If that's the direction you think this is heading, I recommend a compression test and cylinder leak down test. This will prove the integrity of the valve train with far greater accuracy than any scan data PIDs.
Sorry you didn't get any response on your last post.
For what it's worth, it is normal to see a small amount smoke from EGR on just about any car you smoke test. I think we've all seen that early on in our careers and changed at least one before learning that lesson.

Compression tests and leakdown tests are perfect.  The injectors were leaky and have been cleaned.  However, on start up there is no valve tick and the vacuum gauge is rock steady at 24''. As it warms up the tick starts and the gauge fluctuates 0.5-1''. When it is really hot, the noise will sometimes stop and the gauge is rock steady at 24''. Adding a load such as headlights or AC will make the tick louder-turning them off will remove the noise. All ancillaries have been removed and checked. 
I am leaning toward a sticky valve as the car is only used every 6 months and sometimes the engine is quiet.