A key part of how the Mozilla project runs is the Module system, which breaks project activities and codebases down into discrete chunks and assigns an owner to each. The documentation of who owns what is on the Mozilla wiki. So if you want to find out who to talk to about FooBar-ing in Mozilla, that’s the place to look.
If you don’t find the owner of FooBar documented there, then you’ll need to find out who’s in charge by asking around. But once you do find out, please suggest to that person that they head over to the Modules page and get their ownership formalized by applying to create a new FooBar module. It’s not a complicated process.