Apparatus for mixing air and fuel in an internal combustion engine

An apparatus for mixing air and fuel in an internal combustion engine comprises at least two throttle bodies (2a, 2b) having an inlet (3) and an outlet (4) and at least two air chokes (8), each located at the inlet of one of the throttle bodies (2a, 2b) and coaxial with the throttle body (2a, 2b). Each air choke (8) has a portion (9) that is fixed and a portion (10) that moves coaxially relative to the fixed portion (9) between a first position in which the air choke (8) presents a first height (L1) and a second position in which the air choke (8) presents a second height (L2) that is greater than the first height (L1). The apparatus further comprises at least two independent actuators (13) each moving one of the mobile portions (10) between the first and second positions, and at least two fuel injectors (11) located above the air chokes (8).