Well it IS a NA gas V-6, that's 2 things that require higher RPMs, especially at altitude with towing. I towed a 5,000 pound trailer from Ohio to Colorado about a year ago, never saw 5th gear the whole way. Locked it out....of course that is mostly a flat drive.

If power is the only thing lacking...rather than a new vehicle, have you considered getting the supercharger? Plenty of good reviews about it (and videos on Youtube).

Member MillerPKA just had one installed on his new Runner....as I understand it, $6000 for parts plus labor for the install. That is a WHOLE bunch less expensive than the loss you'd take getting a new vehicle.

Here's one video...skip to about 9:30-10:00 for the good discussion.

https://m.youtube.com/watch?v=GbFKMfLeCiw