I am looking at changing the primary jets in my Edlebrock Q-jet. This is due to obvious carbon build up in the tail pipe. The carb I have (Edelbrock #1904) came with .073 jets - what do you guys/gals recommend for a mildly built/balanced Chevy 350? I am thinking of trying .068 to see if it cleans up the exhaust any (might eliminate the slight backfire I have developed when letting off the throttle).