After yet more forum deep-diving, I managed to find references to the power intake valve. My truck is rattling at a slightly different RPM (2700) but it sounds like this could be it.
I can't find a reference to it quickly in the service manual. Is this a DIY-capable inspection and repair? Obviously I don't have the computer to do the check as per the TSB, but if it's not a PITA to get to the intake assembly and glue this thing in place then I don't mind doing it myself.
I do have a Nissan dealership nearby that's been very good to me through the chain tensioner and other repairs, but dropping off my truck and going back to get it is a pain in DC traffic.