 After the dominance of Mercedes , most of the GT1 class competitors chose to not return to the FIA GT Championship for 1999 , leading the FIA to eliminate the category from the series . The Automobile Club de l 'Ouest ( ACO ) , organisers of the 24 Hours of Le Mans , chose to follow the FIA 's lead and no longer allow GT1 category cars to enter Le Mans . While FIA GT concentrated solely on its lower GT2 category in 1999 , the ACO created a new category of race car known as a Le Mans Grand Touring Prototype ( LMGTP ) . The LMGTP regulations for closed @-@ cockpit cars were similar to the former GT1 regulations but shared many elements with the ACO 's existing open @-@ cockpit Le Mans Prototype ( LMP ) category . Mercedes , no longer able to compete in the FIA GT Championship with the CLK <unk> , chose to concentrate on the ACO 's new LMGTP category . 
