Unless you see raw fuel in the regulator, based on what you've reported it's not an issue, move on, and I wouldn't go thru all the hoops to change it.
About changing out cam sensors, I wouldn't bother unless you have a new one in the box to swap with. Not worth the trouble if you're just juggling used ones.
On that subject, I've had issues where during installation, the red rubber gasket inside the connector was doubled up, preventing the connector from reliably seating. Be sure to eyeball the connector to confirm at least, but not more than, one gasket is in play.
Did we talk about verifying the spark plug firing order?
Seems like we've gone over most if not all the common stuf. You may be looking at a compression test and injector inspections at this point. Not looking like a simple fix is going to do it, whatever 'it' is, sorry.