Oil Pressure Warning...
I just changed out the following on my wife's Audi A4 1.8t Cabriolet:
All Spark Plugs
Air distribution breather hose (and o ring) 06A103213AM
I also broke the breather tube (06B103213AK) Instead of replacing this part I used some 5/8 hose and securely fastened it to the breather hose vent (06B103221L) and the PCV (06A103245f).
The car seems to run fine. However I have noticed the oil pressure warning light coming on intermittently, but goes off after a few seconds.
Oil level seems to be ok as well.