I cant find my original thread,but i was having major backfiring at wide open throttle. I trouble shooted several suggestions but still have the problem.Even changed the Edelbrock 600 with a Holley 650. Now im thinking its the adjustable vacumm advance. Could anybody give me some idea how to adjust this as i've not done it before. I know it requires allen wrench into the module for adjusting, but thats all I know.