You can just rescale the inner shell by a small fraction and it will no longer be an issue. I used to do this when I made renders in Maya and some mods had that issue.
So I am having a similar problem with the Aero88 models only. First off, I am VERY new to modeling and am really only working with blender to do basic renders, so assume you are speaking Greek to me (sorry).
The issue I am having is that with the Aero88 models the interior seems to be intersecting with the exterior. The catch is I cannot seem to individually select the interior in order to shrink it (as recommended by Mystical) to eliminate the intersection. When I import the model from carviewer, it seems to recognize it as all one piece. I can only seem to select the interior to add texture to it, but I cannot manipulate it any further than that, and it does not show up as an individual object in the objects list.
I have noticed that the intersection will often occur on TMS renders for Aero88 as well.