about that oil pressure sensor mounted in the plug in head, take care, there is usually lower oil pressure (about -0.5bar) than is in rest oil system (there is pressure limit valve between oil circuit and head).
Not remember what oil pressure gauge you have used, but Audi have dual oil pressure sensors, one part act as classic 0.3bar switch and second part as pressure sensor 0-5bar, this I have used and its mounted at oil filter bracket in original oil sensor mount hole.
MAF works as fuel injection quantity limiter(EGR and rest is secondary use), it limit fuel depend on airflow, you can simply change MAF map (aka smoke map) to ,,flat,, map (all values set to max. value), in this case your engine run like without MAF, but this have one problem, you still need have connected MAF sensor electrically, it is possible to turn off MAF in ECU at all but I dont know how yet
In principle MAF is there only for controlling emissions(smoke) and for normal running of engine is useless
without MAF=more smoke; no smoke=no fun
That engine management can be simplified like this :
- you put throttle to floor = 100% for ECU
- ECU looks in map: throttle vs injected quantity(IQ), for example map returns 40mg of fuel for 100%
- now ECU look in map: injected quantity vs required air quantity, ECU for example get here 1.3bar for 40mg
- now ECU have IQ and pressure, now it looks how must be turbo adjusted to produce this boost pressure, he get value and send this to N75 valve
now can be fuel injected BUT with a lot of smoke because turbo need some time to spin up and produce desired pressure (=amount of air to burn fuel at all), at this time MAF is in action, MAF is checking for income air flow to turbo and limit IQ to archive smoke at lowest level, when airflow raise to required amount (and turbo produce required boost) fuel can be injected at full amount.
Of course this is very simple description, there is a lot other values what affect this procedure like water temperature, air temperature(it affect density of air/air pressure/amount of air...),atmospheric pressure, rpm, real pressure in intake or need to be calculated (injection advance,required time of opened injector to inject requested amount of fuel, engine load..)
Of course EGR needs MAF also, there is checked how much air goes over MAF and compared with MAP vs IAT and calculated how much amount of fresh air can be replaced/filled with exhaust gases.
Take this as simple description for what is used MAF