High Quality Content by WIKIPEDIA articles! The 1991 Camel GT Championship and Exxon Supreme GT Series seasons were the 21st season of the IMSA GT Championship auto racing series. It was for GTP and Lights classes of prototypes, as well as Grand Tourer-style racing cars which ran in the GTO and GTU classes, as well as a tube-frame All-American Challenge (AAC) class during select rounds. It began February 2, 1991 and ended October 13, 1991 after nineteen rounds.