MEP Troubles

MEP is proving much more of a task than I had previously assumed. It can be pretty confusing deciphering the plans on what goes where. Though this won't necessarily count toward any takeoff numbers, I still would like an accurate depiction of the supply and return air systems. My main trouble comes in identification of a few elements and ensuring I am placing the right component in the system. The first floor is basically finished, and I began work on the second floor's supply system.

After clarification I will be designing a few elements of piping for Plumbing system as well. If I can finish up the MEP systems, I can go back to the previous models and edit/alter everything for better appearance.