Since the 4cyl capability and power comes up from time to time, I thought I offer this experience. I'm not presenting the 4cyl is as capable as the V6, but I am presenting what my particular experience was.
99% of the time my truck is in the city on short runs with 1 day of lawn maintenance hauling a 2,000 lb load. It does that great.
This past week, I decided to use it for a beach trip. The truck was "loaded".
I basically hauled a bed full of luggage and 2 bicycles, and another bike on the roof in a Yakima Raptor. 300 miles of the trip two-way were with 4 persons through the I40 and hwy 70 in North Carolina.
Much of the time the posted speed limit was 65 and 70 on flat or low rolling hills. I traveled with traffic speed. The engine tac'd between 2500 and 2750 with a "few" 5K revs to negotiate traffic.
The truck did fine. It held highway speeds very well and I think I only had to push it once in the trip. Accelleration was the biggest thing but, even without reving the engine heavily, I managed not to impede traffic. Sure there were some cars off the line faster but I got up to speed respectably.
The mpg was somewhat hit by the factors. I eeked out 19mpg.
I have made this trip with a lighter loaded 01 v6 4Runner which purred through it and averaged about 20mpg, but I have to say considering the load, the 4cyl did well enough for me to take it again. I hauled a load of stuff.