MII QoS Messaging down from a system like PI or back up to a system like PI? For down from PI be sure to follow the documentation here:
Message Listeners - Message Services - SAP Library
and here:
Quality of Services - Message Services - SAP Library
For back up to a system like PI see the documentation here on the XI Post action which is used for QoS integration back to SAP PI:
HTTP XI - Content Development - SAP Library
Hope this helps,
Sam