there were a few topics on oil pressure in the past already.
this were some of the answers
1. could be a dodgy gauge
2.Oil pressure on Alfa's aren't to correct
3.even tarquini in his DTM car haven't managed to put the pressure above 4b
My 155/8v pressure is 'round 3-4 bar when cold and as soon as the engine is hot you have really to push hard ,say above 3500 rpm to get that kind of values again , when on idle speed (warm engine) it drops at the marker.
When I first had my car it worried me also , nowadays I don't care anymore.
The only thing I do is a weekly oil level inspection , keep the level always on high...