I suggest you replace all the 8 coils and see what happens. If you still run engine so hard, it will damage the engine irreversibly. Remember, when you test the car, do not push it hard.

Sounds quite simple from what you've said.... if you have oil in the coils then you are simply shorting out the spark, causing loss of power and misfire. No major damage should be done as fuel mixture is simply washing the bore and being exhausted.

Obviously you don't want this to go on very long as washing the bore eliminates lubrication, so as others have said, DON'T DRIVE until you've found the cause.

Cheers

I would say it is you're valve covers leaking oil into the plug holes shorting the spark to ground this can make a car miss stumble hesitate shake all kinds of problems I would change the valve cover gaskets and clean the coil packs with brake cleaner make sure the plug boots fit the plugs tight if not replace them oil will swell them up most likley the coil packs will be ok good luck.

Like I said before, your X is in need of maintenance, asap. Valve cover gaskets for sure, and not only that make sure you change all of the washer, because those also tend to leak into the coil bay. The washers are the one's that you screw in the valve covers. Trust me, I had my valve cover gaskets done and they didn't change the washers, oil still leaked into the bay. Good luck.

Thank you Bimmerdude again for the support,much much appreciated.
Tomorrow we will clean the oil from the coils and gaskets. My mechanic talks about some sort of rubber joints,are them the same thing as you're taking ? Should we replace all 8 coils or the ones that seem faulty.
For now we've replaced:all spark plugs,engine oil,2 lambda sensors after the catalytic converter
I will definitely make some pictures of the engine/coils/gaskets etc and post the pictures in here so maybe some of you can see the exact thing.

I really count on x5world as the last resort for help...

I would clean up the coils and replace the rubber plug leads (short rubber things from coil packs to plugs) and then see how it runs. That, plus the gasket job may be all you need.
GL.

Yep, that is correct, rubber joints. Change those as well, since you have to take them out anyway. Good Luck, and yes post the pics. Let everyone know what happens. Good Luck...

Cylinder head gaskets are the source of problem, then the coils.

We're starting to fix them today at 3pm local time...4 more hours to go...we've purchased what was needed....very reasonable cost for all the rubber joints...95Euros
Hopefully i'll be able to post the pics later in the evening
Regards,

Yes post the pics. Good Luck...