i konw this is not a volvo but electronic injection is not different from every other car.

I have been experiencing a intermittent loss of power.
No fault codes found. Not even when the car runs. never the light on.

I have a C20XE(aspirated 16 V) Motronic 2.8 with a DIS.

I replaced with new parts from Opel :

-cylinder head
-valves
-catalitic converter+ central part+ final part
-DIS+ cables+ sparkplugs
-Fuel pump+ fuel filter+ fuel pressure regulator
-knock sensor
-Air meter sensor
-Water temperature sensor
-Air temperature sensor
-throttle position sensor
-O2 sensor
-cam shaft sensor
-air filter

I cleaned all the wires, i checked the compression and it is perfect.
I didn't replace the injectors ,ECU and the cranck shaft sensor.

Sometimes the car goes very fast and you feel it pushing you back in the seat.
Sometimes else it goes smoothly slow with no pushing.Takes ages to rev high.
When this occur the tester read all the parameters within the specs.

Do you think is a ECU problem? or the cranck sensor? or injectors?
please help me
thanks a lot
Simone