I'll assume this is for a 2.4L?
There's four hoses... one big one goes to the metal crossover pipe which connects to the brake booster.
There's a not-quite-so-large one which is the EVAP solenoid (mounted by your a/c compressor)
The two small ones are for the FPR on the end of the fuel rail, and the other goes thru the harness to the passenger compartment, ultimately going to the heater controls to provide vacuum to change the heat/cooling vents. This isn't present on the 03-05 Ecotec as they're cable controlled.
if the spot on the t/b where it is supposed to plug into was open and not capped off yes.
