Variable length intake AKA "secondary". The "butterfly" valves open when you "gun" the engine providing a more direct path for air into the lower intake manifold thus increasing power in high throttle situations. The longer intake runners are more efficient for low end. Mine are disabled with no noticable difference in performance. If they dont move then the shaft wont wear out.

The majority of V6 sports came with the 3.0 with only the rare limited model that came with a SOHC 3.5 that does not utilize the same intake plenum as the 95-96 Montero DOHC 3.5.