I know this might be unrelated, but it is to do with cutting out / power problems. In my Alfa GTV, I had a problem very similar to the ones people have been describing. There was no problem with revs dropping, but if you came over bumps or floored it especially uphill then the engine management / fuel injector warning light would come on (and stay on for 5 minutes on one occasion). The first time this happened the dealer did as somebody has stated change the lambda sensor as this is part of the fuel injection system. In my case it was responding too slowly and hence when a power increase was required was not able to deliver it as expected, hence the warning lights. The second time (and much worse) they traced it to a faulty potentiometer in the fuel injector circuit which the changed and now, no problems... Oh, those Italian electrics...

Cheers

Andy