Based on the FLEXJET NHRA Factory Stock Showdown performance numbers from the Texas NHRA Fall Nationals at the Texas Motorplex in Dallas, TX, the NHRA Technical Department is reducing the supercharger overdrive by changing the upper supercharger pulley for the 2019-2023 Chevrolet COPO from 3.250 inches to 3.375 inches. The minimum weight will also be increased by 25 pounds, from 3525 to 3550.  This rule change will go into effect immediately. NHRA reserves the right in the future to make additional rule changes to control performance and maintain parity in the category.