Mirrored object

 From:  Fitz (3DARTZ)
Hey guys,
so, Im working on a car model and I mirrored the door to the other side of the car.
on export, both doors have thier normals pointing the correct way. out.
then I build a side view mirror on the original door and joined the pieces where they meet
so they are now 1 object.

I deleted the door on the other side, then I mirrored the new door with sideview mirror on it.
Now upon export the original door comes out with normals pointing outward
and the mirrored door has normals pointing inward.

How do I fix this so it exports correctly.

Mike Fitz