Oil Pressure Sensor location on 12V 2.8V6

["C. Krafft" <ckrafft@olg.com>]

The Audi gods seem to be taking their wrath on me.  After changing my O2
sensors on my 93 100CSQW, the engine coolant light went on.  After a trip
to the shop to locate and change that sensor, three days later my engine
oil pressure warning light comes on.  The analog gauge reads 4-5 bar at
idle, and the level is normal, so I suspect the sender unit may be sending
bad info.  Question is, where is it?
Anybody have experience with this problem?
Car ran very rough when I started it up this morning and stalled out a few
times, before I decided to take another vehicle to work.  Normally starts
and runs without a hitch.
Thanks,
Charles Krafft