Groaning/gurgling at low RPM (2009 4.0L Prerunner)

Hey folks, over the last few months I’ve been trying to diagnose a throaty groaning noise at low RPMs, specifically between ~1,100-1,300 RPM. The noise occurs in drive (and sometimes in reverse) when my foot is on the accelerator. It occurs irrespective of speed.

My initial thought was that it was trapped air in my coolant system. I recently flushed and burped the coolant, and I am now confident this is not the issue. I then tried replacing the engine air filter. The rubber lining on the filter had begun to fall off, and when I replaced it the noise went away for a full week. But now, the noise has started up again and I’m at a loss.

I am wondering if it is just a low-quality engine air filter. I just bought an STP 9623 filter from AutoZone, which is what I had before. Is there a better quality filter out there that has a better seal? Of course, I might be misidentifying the issue, has anyone experienced something similar?

This thread sounds like the same issue, but it doesn't look like they found a solution.
https://www.tacomaworld.com/threads/help-strange-gurgling-sound-at-lower-rpms-06-4-0.313123/