Only FIA RGT-cars allowed in Ypres. Cars with national homologation were allowed a few years, but as mousti said it wasn't a success. According to some GT drivers back then the organizers didn't have any respect for them. For example, at TC people often even didn't knew that GT cars were coming after the ERC-field, and nobody was there anymore... After that some GT drivers agreed to not drive in Ypres again.