Yes I am in fact refering to the 1995-1996 ITC series which featured cars called Class 1 they were 2.5 V6 N/A engines 12000rpm limit 500bhp based on road cars with 4WD. 1000kg-1040kg. Opel Calibra, Alfa 155 and Mercedes C Class (RWD).
www.redshoes-archive.com/Touring_Cars/ITC/. As for GT1 my fav cars were the Porsche 911 GT1 98, Mercedes CLK-GTR and CLK-LM