Can't say for sure without seeing it, but it sounds like a part of the PCV system. That will bring blowby gases into the intake system to be burned. If the other end attaches to the fresh air tube coming from the MAF sensor, it is supplying air to the crankcase and the air will be cold. More likely it's bringing the blowby from the crankcase to the air intake at the throttle body since that's where you said it is attached. A rubber tube would work but oil vapors tend to cause it to deteriorate very rapidly. Being metal suggests oil vapors, hence, part of the PCV system.
The tube can't be part of the EGR system because the hot exhaust gases aren't introduced at the throtle body, and that sad plastic clamp would melt.
If this pipe slides onto fittings at each end, you might find replacement hose in bulk at the parts stores. If there are special ends, bolt-on flanges in particular, it is more likely to be a GM-only part. Still doesn't hurt to ask at the parts stores.
Friday, March 12th, 2010 AT 10:05 PM