Car won't start, does not suck air when engine turning over trying to start has spark, fuel & compression als?

The car was running great the day before, it has since been checked for spark (all cylinders), compresssion (all cyl.in limits) Gas under pressure at rail & injectors. new plugs & wires & battery. Turns over strong but makes no attempt to start & (only clue)-NO Suction at throttle body air duct. Front cover pulled & timming gears alligned and cam&crank keys good. Help