Also remember, if the TD/DPI is on the last timed down of the 4th quarter, the foul MUST be marched off on the try (if there is one). The rule for enforcement of a foul on a TD scoring play specifically says the "succeeding kickoff", so it can not be carried into OT.
If the DPI foul occurs on the try, though, that can be carried over, since the rule states "succeeding spot" for a try.