I have two AVS2 1906 carbs, which are 650's, I then put boosters in the primary sides out of 1902's, which are 500's. These boosters knocked 100cfm out of each carb, giving me 550's with large secondaries like a Thermoquad somewhat. If I need more, I will put in the 650 primary boosters, this way I'm not pigeon holed on maxed out 500 cfm carbs. Any advise or comments on initial setup most welcomed and appreciated. If the OP feels I've hijacked his post, apologies.