Abstract: A staged multi-barrel carburetor (C) has two air induction passages (P) and first and second throttle valves (T1,T2) one of which is positioned in each of the respective induction passages. The first throttle valve (T1) is operable to open prior to the second throttle valve (T2) opening, and a countershaft (CS) is interconnected with the first throttle valve for rotation therewith as it opens and closes. The countershaft is interconnected (1) with the second throttle valve to open it as the first throttle valve opens, but not until the first throttle valve has opened to a predetermined open position (15). Opening movement of the second throttle valve, after the first throttle valve has opened to its predetermined open position, is delayed (21) if engine vacuum exceeds a predetermined level thereby to prevent lags in engine performance which may occur during engine acceleration.