When in question, LB PF or DB PF?

[Morningrise]

Suppose B commits a personal foul against a defenseless receiver at nearly the same time as - or perhaps a fraction of a second after - the pass falls incomplete. On fourth down. Is there a when-in-question guideline for determining whether this is a live-ball foul or a dead-ball foul?

[JasonTX]

Considering the guidance we have for the "cheap shots" that happen behind a TD scoring play.  When in question the foul occurred after the TD and not before.  It seems they are giving the benefit of doubt toward the offense.  Using that, I would suggest you treat the foul in your pass scenario as being a live ball foul.