Holley/Demon Carb stumble

12.8:1 compression HYd roller cam 408.
4200 stall and 4.56 gears out back.
Race Gas
This is a good used plug after 30 passes VP race gas 12.6 compression carb dialed in max mph, 12.4AFR WOT O2 with short extension

408plugIMG_2729.PNG