Sounds like you need to remesh your object. I'm guessing you'r working with nurbs or some kind of spline based design (the only cad-centric program I've used was Rhino).  So when converting to polygons, you'll need to aim for lower mesh resolution. How you go about that would be in your docs I wager.

If that's not an option or not the case, you can try loading the OBJ file into UVMapper and saving it again without Normals.  This will reduce the file size significantly.  Make sure all your normals are facing the correct way first.

The reason the 3DS file is crap is because the 3DS format used is the same Poser uses and most other apps use outside of Max itself.  It's the 3DS format from 3DStudio - not 3D Studio Max, I'm talking 3D Studio - the original.  So you can guess how old and limited that format is. It also has a polygon limitation of 35,000 polygons per an object, so if you're exporting something as a whole that contains more than that, the format will break it up into smaller bits.  Usually with no rhyme or reason.

-Teyon