Opel Zafira engine problems

[drakkie]

My uncle and many friends of my parents drive a Opel Zafira of a couple of years old.It seems like these engines have a fundemental problem.after driving for a while (45 minute plus) the egine suddenly slows down a bit,without them having lifted the throttle.they went to the dealerships and had the Zafira examined.my uncle has had the following parts changed to new ones without result:

Throttle body
complete engine management system
sparkplugs
fuel pump
part of the injection system (verstuivers,sorry no idea bout the english word)
and some more smaller parts...
the car has been sent to the dutch importer where they took it completely apart and couldnt find anything wrong.

the mechanics were stunned and had no iea, but now this problems is emerging much more, since people are getting a higher mileage.the problems occurs first around 140.000 km.he always had his car reguraly serviced by the official dealerships and so did all the other people that did.

I am just warning you fellows, since this can cause dangerous situations on the highways..