Power/performance/stalling

Hi,

What occurs is that starting from warm the performance ie, acceleration is sluggish.
If the revs are not high enough it will cut out from a standing start or stall when coming to a stop or braking suddenly.

Under idle the revs will fluctuate too. I've noticed that from cold it idles uniformly at just under a 1000 rpm but as the engine warms up or from restart of a warm engine it fluxes between 500 and 750 rpm.

The problem may have manifested itself after a routine oil inspection. I cannot remember for sure.

The oil light does come on randomly for a few seconds but disappears almost immediately and after stalling the engine does restart ok although it takes a few seconds longer than normal.

All of this points to an airflow/pressure problem but could just as easily be electrical. I've seen solutions ranging from software updates of the computer, to replacing fuses, searching for ash deposits, changing coils, oil pressure, fuel pressure etc etc. The list is endless and can only really be solved with putting the car on to a scan tool and seeing what it comes up with.

The problem I have is that I don't trust garages.
Many will just turn around and say "you need a new computer and that'll £££££££ thousand please"

Is there anything that I can do to perhaps solve the problem before resorting to more expensive solutions?

My car is a 2001 BMW 320i and the miles on the clock are just coming up to 90k

Thanks
Mark