S4 BBK 4.2 V8 technical advise needed.

[VAGMAN]

The 2003 Audi S4 Avant was taken of the road the day I noticed suspected chain rattle / clacking under light revs or load alongside can shaft position fault codes & has stood unused for a few months.
I'm now trying to get to grips with the required repair but I am having a few issues where another's input would be appreciated.

Since being stood it has a few electrical issues after complete loss of voltage from the battery. It now has been fitted with a good quality replacement. Since however the Red engine oil warning is on alongside airbag fault, no rev counter, or speedometre or back light from the cluster. The fuel and temp gauge are functioning after resetting by pulling the fuse.

Note car is being run as little as possible Incase oil pressure either low low or high causing substantial engine wear.

I was entrigued by the oil pressure fault (wishfully thinking low pressure could be the cause of my timing issues as tensioning a and adjusters are hydraulically governed by oil pressure so i checked oil level, fine there. Replaced level sensor (foolishly) in sump alongside new oil & filter.

Checking the oil pressure using my gauge i had a cold start reading of 65 psi/ 4.4 bar! Way above expected according to auto data of 2.0bar/2000rpm. At operating temp it dropped to 2.0 bar at idle. I'm not sure if it should be less at idle and only reach 2.0 at 2k rpm? Not sure how to interpret that? Any help appreciated there.

I also noticed the the pressure switch in only rated 1.2-1.6 bar?

Ok so electrically I have codes staying incorrect vin for the instrument cluster (no rev / speedo / lights etc...?) & also in airbag module (fault light displayed) could this mean the cluster could throw the oil warning un-necessarily? Wasn't presented when car was put out of service due to timing concerns only after bringing in and fresh battery.
Needless to say I fitted new pressure switch, oil light remains, even when warm started.

I know the pump is driven by a auxiliary shaft from the timing chain but assumed as water pump, PAS was all functioning it was still being driven.

Why would I be seeing elevated oil pressure?
Can't be timed in with chain surely and fault be caused by incorrect engine timing.

If oil pressure is incorrect what impact does this have on my hydraulic tensioners & cam shaft adjusters?
If timing chain, guides &/or cam shaft adjuster fault why or how would that effect oil pressure.

Realise I waffling on but need someone with a good knowledge base to advise if possible.

Thanks in advance.

[VAGMAN]

Also note that compression test was carried out on all cylinders and results are as follows:

175 175
165 175
175 175
160 175
Front

Just thought it might be of use to anyone contemplating the issue.