After the first "gas shortage" hit, a very popular "trick" for those guys with quadrajet ( quadrabogs) carbs was to replace the base gasket with a homemade one that only had holes for the small primary venturies. This "trick" resurfaced afew years back when guys were mounting dual quad setups but the rear carb was setup as a dummy by doing the same thing, a full gasket with no openings - so no airflow.