You can't retrofit OBDI in OBDII car,but you can use flash code reader for ECU and ECC since '96 850 T5 have M4.3 management which still produce flash codes.
All other modules are fully OBDII.

What oil viscosity you have in the engine?
What oil filter you installed?

If oil is too thin for the mileage and condition of the engine...oil pressure will not be adequate.

If oil filter is something aftermarket without built-in check valve....oil pressure will be compromised.

5w-30 and 10w-30 is too thin for the car with that mileage. 5w-40 or 10w-40 would be more adequate. Both of those oils have the same viscosity when engine is at operating temperature(xx-30 index). You might have a problem with oil pressure...but there is a possibility that the light is shorting some...

I'm not claiming that higher viscosity oil would solve your problem,but there is possibility. You should be able to test oil pressure before throwing money again on something you just replaced. There is some gauge which is screwed into the pressure sensor hole while engine is running. That would cle...

It doesn't seal well...that's why you have high idle.Engine is sucking "false" and unmetered air.
Did you re-connect flame trap flange and hose on it?
Also...check that ribbed hose for air induction between maf and throttle body is tight and have no leaks.

Why that MAF sits upside down?

Air pump works for a few seconds after starting a cold engine and sometimes at prolonged idle when ecu ask for it. You can delete SAS and still pass inspection with soldering a diode in ecu and leave everything as it is. If your problem is SAS valve,you can also block it and leave all components in ...

I was referring on gray one when someone said that they are born bad.
It seems that someones experience is that grey one should be replaced with green.

They should turn off immediatelly after the car is locked.
Otherwise...they turns off after a minute or so.
There should be three positions of the switch...always off,on/off with doors opened or closed and always on.
Check if switch is in proper position.

When they are on when you unlock the doors,they should go off after a minute or so or immediatelly after you turn the key to pos.II.

There is a timer relay which controls those lights,but i don't know where it's located.

ET 50?
Nope!
ET 49 is the highest offset which can fit 850 and NOT wider than 205 tyre with this ET.

No problem if you install spacers.