Ok I figured out my problem it was with the paging toolbar. I needed to change the toolbar store to use ext.getStore and everything works perfectly now! Thanks for the great Plugin!

Code:
 bbar: Ext.create('Ext.PagingToolbar', {
            store: Ext.getStore('mfgCombo'),
            displayInfo: true,
            displayMsg: 'Displaying {0} - {1} of {2}',
            emptyMsg: "No data to display"
        })