Rapidly fluctuating oil pressure and rough idle

[Brian300E]

Well this problem has been driving me crazy, and my mechanic can't seem to figure it out either. When the car is warmed up, in drive, and stopped somewhere such as a stop light, it has an extremely rough idle. The oil pressure fluctuates rapidly between the 2 and 3 bar, and the car has a rumble-like shake. This problem still occurs despite the fact that I have just had a valve job done and replaced the injectors (o-ring, guide seal, etc.). I have absolutely no idea what it could be, and I want to suggest something to my mechanic so he doesn't blindly guess at what the problem is.

I have checked a previous post 300E rough rough rough idle and it suggests that the EGR may need to be tested. Even though some of the symptoms are similar, it doesn't address the issue of the fluctuating oil pressure, which makes me think the problem with my car is different. The car idles fine when cold, but when it warms up I have the problems described above. I would appreciated any help, because I am totally lost on this one.

Regards,

Brian