I think there is one that goes to the EGR valve. Could that be the one you're referring to?
For the A/C compressor, usually they ain't cheap. I think A1 Cardone makes a decent one. I'd call Advance or Checkers/Schucks/Craigen for prices, they usually offer very good reman products w/warranties.
However, try a junkyard, just make sure to have it checked out first.
