Hi Marc, yeah it's pretty common for polygon sub-d modeling programs to kind of treat sub-d surfaces as just a way to take some polygons and generate more polygons, rather than actually focusing on dealing on the actual smooth "limit surface" itself...

- Michael

I've done a quick copy of your plug and a video of how to get better results with ViaCAD v7 for this task. It's not perfect, but it might help you along a bit if you can't find something better at a reasonable price.
I've attached an Illustrator and a DXF file of the plug for you to look at.

Martin.

http://screencast.com/t/VmxGbV6lVI

To get this so called two-line-weight renderings I currently use Cinema4D and Sketch & Toon. To get the thick outline rendered properly all individual objects of the plug must be connected in C4D. I attached a sample rendering. If I somehow could download the plug model I could post this too.

Although C4D + S&T works very well I would prefer a direct workflow from MoI to Adobe Illustrator that would give me the same result without much work. Especially because the illustration would remain in vector format. It would help a lot if MoI (optionally) didn't export hidden lines to the .ai format.