@Sgt Nuts
Is this holding back at 3.5K rpm every time now?
Have you got any way you can check the ignition timing advance?
The rpms at which the car holds back are not fixed. One minute its from 3500 rpm, the other it's from 5000 rpm. I have the feeling (but cannot prove yet) that it happens the second the fuel system goes into open loop.
I can say for sure that it's not the moment that I start accelerating. Always whem rpms have been climbing rapidly for a few seconds.
I think my scanner is able to record the sources that I tell it to. Should be able to record open/closed loop and ignition advance. Will try to get a reading.
I did what you suggested earlier btw, drove the car a bit without the fuel cap. No change.
Did find out that there's some kind of EVAP system in the car that seems to regulate fuel tank vapours and feeds them into the engine. Some carbon cannister in the right front wing with a small electric valve. Seemed to be clicking rapidly once I put the car on ignition.
Not sure how this system works or is supposed to work though.
The line coming from the evap canister goes into a thule on the rocker cover. When I take this line off the engine revvs up quite a bit, so it must have some connection to the intake manifold.
Seems to me it could be a source of air going into the engine without being detected by the MAP sensor?
If extra air was getting into the engine through this pipe I can imagine that the O2 sensor would correct the extra air it detects by injecting quite a bit more fuel. Once the fuel system reaches open loop, the O2 sensor is disregarded and the ECU uses a predetermined map which might not compensate fuel to the level the O2 sensor has been doing up to that point..
Might block the line off for a testrun, see what happens