Complex sentence: The GTU class did not participate with the GTP and GTO classes in shorter events, instead holding their own separate event which included touring car competitors from the IMSA Champion Spark Plug Challenge, but did not race for points in the IMSA GT Championship.
Split into simpler sentences: The GTU class did not participate with the GTP and GTO classes in shorter events, instead holding their own separate event which included touring car competitors from the IMSA Champion Spark Plug Challenge. These touring cars did not race for points in the IMSA GT Championship.