Ours has lived on a diet of Shell V-Power (99 octane - not technically required based on the comp ratio but good fuel) for most of its life - we got very occasional pinking with the OEM exhaust when lower grade fuel was used esp in France and none at all since we moved from OEM to G56 exhaust system - conclusion from our perspective is that good fuel will help but the restrictive OEM exhaust is the key issue. Sorry to hear of Rik's troubles - sounds like his car might have missed out on the various cam box upgrades...
