I have created duct systems and everything works out well until I needed to remove a diffuser. when I removed the diffuser and associated duct/fittings the CFM for the system did not adjust to the new CFM. when I deleted just the diffuser the same thing occurred. However when I deleted just the fitting the CFM changed. I see nothing the family that would suggest it has a flow value associated with it so once the fitting is removed from the system it should correct itself Right? I'm I doing something wrong or is this another "feature" of Revit?