Krisemann wrote: ↑30 Dec 2019, 06:45 However, if I let the car idle for 10-15 minutes before driving, the car runs perfectly.

In other words: No power when cold.
Check for intake manifold leaks when the engine is cold.
A defective Coolant Temperature Sensor could throw off the Air/Fuel mixture.

IAT sensor have exactly the same spec as ECT.
Multimeter is all you need.
A2 5-1-2 :
https://www.scandcar.com/volvo-850-error-codes/

You have a vacuum leak somewhere or o2 sensor connector is bad.
FPR-fuel pressure regulator should be checked if it leaks fuel into vacuum line.

No lighter!
For Map you measure voltage while applying a vacuum to it's vacuum line and voltage at rest.
YouTube have a lots of videos on how to check Map sensors.

For IAT you measure resistance,just like for ECT.