I'm assuming this is an 07? If so, it is a known issue and MC will replace your rear hatch under warranty. The motors changed ever so slightly with the cats this year and that little plastic fitting on the top of the manifold hits the edge of the cutout in the bottom of the hatch. Again, they will get you a new hatch under warranty with the proper cutout for this.
Sounds like your dealer is either unaware, or jerking you off. Contact MC if you have to. Took about 5 weeks for MC to get a new hatch matching my interior colors to my dealer.
Edit: When you get the new hatch installed, you will immediately realize how dirty you've let the rest of the interior get.
Edit 2: I can take a picture of the underside of the new hatch when I get home to show your dealer if they really don't know about this, but they should.
(Message edited by Stanfield on February 08, 2008)