Abstract: An air intake system for an internal combustion engine having a load controlled port throttle system. Specifically the air intake system includes an idle speed control assembly (30), with a metered air line (28) supplying air to a slide metering valve (32). Idle air lines (34) lead from the slide metering valve (32) to the intake ports (16) downstream of the throttle valves (20). The slide metering valve (32) includes a slider plate (50), which can be moved by a solenoid (42) to maintain varying degrees of alignment with outlet passages (48) to the idle air lines (34). In this way, precise amounts of idle air are metered to the intake ports (16) with equal cylinder-to-cylinder air flow and without substantial cross-communication of air between cylinders. A vacuum assembly may also tap into the idle air lines (34) to provide a stable source of vacuum for other engine components.