This is the PCV (Positive Crankcase Ventilation) breather box for the 2.2 Turbo III engine.  If you own one of these cars, you know where this goes.  It's located on the front (center) of the intake manifold and is tucked behind (around) your vacuum lines (just under the fuel rail).  These are great at separating engine oil from the crankcase vapors and making sure not to let engine oil make it's way into your intake tract.