Paul's use of the Preposition dia with the Accusative

Romans 15:16 (NRSV: "because of the grace given me by God") has led me
to research Paul's use of the preposition dia with the accusative case.
This text is most widely construed in the manner of the NRSV, using
the translation "because".  To some extent that is ambiguous.  Does
Paul write because, at some time in the past, he has been granted grace?
Or, does Paul write Romans "for the sake of" carrying out the grace
given him?  In the second instance dia with the accusative conveys
the final cause (to use Aristotle's categories).

Other problematic texts in Romans are 4:23-25, 11:28, and 13:5.

Does anyone know of a good discussion of Paul's use of this preposition?
Is the construal of these texts left entirely to the whims of the
interpreter and/or translator?  

I would appreciate your responses.

Calvin L. Porter
Professor of New Testament
Christian Theological Seminary