Pest

I would guess Weight Distribution.

Homer: That's a nice setup you got there

wormhole

Well, apparently there were no 5x10 trailers in the state of utah so I ended up with a 5x8 that fit my stuff just fine (still some room left).
Overall, my 4runner did pretty good the only times that I could really tell that the trailer was there was going up hill and on crappie roads (US 95). I kept it pretty much at 65 with O/D off 90% of the time and the a/c on (expect for going up hill). On some uphills my 4runner struggled to stay at 55 pulling around 4500 rpm and on other hills it held speed.
There were numberous other people towing uhaul going at least 75. Heck, a jeep liberty held speed up the hills better than my 4runner but they had a 4x8 and I don't think that theirs was as full as mine. Any how here is how my gas mileage worked out:

Miles Gallons of gas
134.8 8.653
158.1 8.349
113.6 6.804
119.5 7.189
113.3 7.815

Totals 639.3 miles 38.81 G of G
Avg. MPG 16.4725

I filled up with gas when it reached half a tank. The only thing not in that calculation is the tank I'm on now (won't fill up until tommorrow)
Good 4runner