UK Car Repair: loss of power, throttle position sensor, fuel pressure regulator

Question
I have been experiencing a intermittent loss of power.
no fault codes found. Not even when the car runs. never the light on.
My car is a vauxhall  aspirated engine with a GM engine.

i have a C20XE end 1993 ,  Motronic 2.8

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.
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? Or the ECU wiring?
please help me
Simone


Answer
If it was a problem with .........
Knock sensor
Air flow meter
coolant temp sensor
tps sensor
O2 sensor
cam sensor
crank sensor
you would normally expect the engine management warning light to come on.
You say the light not on?
Sounds like you checked all the obvious things, maybe try some less obvious things like.......
look in the fuel tank and make sure nothing blocking the fuel.
try another DIS pack.... they can cause faults with no light coming on.