We needed to keep the Intel USB 3.0 drivers in a Windows 7 reference image.
- Import the drivers into MDT and create a selection profile.
- Edit the TS and update the Injected Drivers step to point to the selection profile.
- Open and edit Unattend.xml. Add the component called Microsoft-Windows-PnpSysprep to Step 3 Generalize.
- Edit the PersistAllDeviceInstalls option to be true.
- Save the Unattend.xml file and close.
More information here: http://technet.microsoft.com/en-us/library/ff716298.aspx