The TSB that kevera posted above says it is for 2003-2005 Vibes. Mitch has an 06, so the assumption would be that the new version of the catalytic converter (the one less prone to sulfur smell) is already installed, replacing it with the same new version likely wouldn't help. However, I wouldn't necessarily assume that it does in fact have the new version. Might depend on when in the model year Mitch's Vibe was built. The TSB is dated 11/17/05, that should have been a few months into the 06 production run.Unless Mitch drives a lot, his Vibe should still be under warranty. That would include the converter, and would also include the AC system. The dealer is being evasive saying the AC system is not covered under warranty, unless the whole car is out of warranty for some reason.There have been three types of catalytic converter failures reported here on genvibe. -First, like mine , was the converter not working correctly, not converting. This one will cause a check engine light, set a code for P0420. (supposedly other things can also cause a P0420) Doesn't cause sulffur smell though. -The second is the sulfur smell problem, covered by the TSB, and does not cause a check engine light. -The third is the clog problem like pmh013 had, gunked up, restrivcted air flow, terrible gas mileage, no power, and again, no check engine light. Don't think this one will cause excessive sulfur smell, might though.So no check engine light is no guarantee that the converter is fine. I'd suggest trying a different dealership, perhaps one that wants customers to come back satisfied, not go away frustrated.
http://forums.genvibe.com/zerothread?id=8344 is the long thread about the sulfur smelllast fall, in
http://forums.genvibe.com/zerothread?id=26039 tnpartsguy posted about having the sulfur smell in an 06. tnpartsguy, what was the resolution to that problem in yours?