I think your problem is that the color intent is a item property, but the document handling select is a device property. I don't have my WIA code in front of me but will probably be something along these lines
Scanner.Properties("3088").Value = &H4
instead of ...
Scanner.Items(1).Properties...
Also, the document handling select is a flag property, here are the const values from wiadef.h
const FEEDER = &H1
const FLATBED = &H2
const DUPLEX = &H4
const FRONT_FIRST = &H8
const BACK_FIRST = &H10
const FRONT_ONLY = &H20
const BACK_ONLY = &H40
const NEXT_PAGE = &H80
const PREFEED = &H100
const AUTO_ADVANCE = &H200