FiTech EFI system
That strange looking thing is part of the vent system, all my fuel system was shoddy and I replaced it all except that vent system tube thing. I had no idea if it was good or bad but it seemed to work. If I had problems it would be the first thing I looked at. There is alot of tubing in it that could be clogged. I checked that they all passed air thru them, it has different length tubes in it so if the tank vents from any corner based on how the car is parked on a hill one will always be upstream. I have since eliminated it for the FiTech system. If you want more info on how this convoluted system works download a Factory Service Manual.
I really like your Dart.