Annular vs downleg boosters on carb

The 950 I ran had down leg boosters, so does the 1.59" BX4 currently on my car, both have been great. As Dwayne mentioned it's all about venturi diameter, IIRC the 950HP had a 1.38" venturi and the 850 was 1.56". From my understanding the annular booster will take away some cfm in the carb and probably why he told you it would give you the signal you want.

I robbed the 950 to build the BX4, but if I can come up with metering blocks and a good 1.75" base plate I'm going to build the 950 to test against the BX4 in the spring.