What savory flavors would pair well with chocolate pasta?
Hmmm, I would turn to cultures that use cocoa as a savory ingredient. There is quite a bit of Mexican cooking that does this and you did mention wanting to incorporate chili powder. How about looking at the ingredients in Mole sauce for an inspiration. Not sure I can provide specifics but just trying to give you some ideas. Mole is pretty intense so maybe temper it with a cream? 

Just some idea suggestions for a starting point.