It would be helpful to know what vehicle it is in and how heavy,gearing trans type(and mods if its an auto).Also which intake are you running?..I would say a 600-650 cfm at sea level depending on usage...Since you already have the avenger throw it on and see how it works...I'm not sure how altitude affects carb sizing..Maybe you need a larger than normal carb with the thinner air?

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1968 mustang..408 windsor.Vic jr heads and intake.Pro Systems 950HP holley, 1 3/4 hooker super comps,Custom CI solid roller camshaft,Probe shaft rockers, 4 speed with 4:11 detroit locker.