Dan, do you have wide tow mirrors on your Tacoma ? If so, you should be able to sight down the sides of the trailer.
Next time you re towing, at highway speed, hold the steering wheel totally straight, and sight down the side of the trailer. You may see it very slightly "moving" side to side. Note I did not say swaying. We'll call swaying an uncontrolled and increasing amount of side to side movement. Which is of course bad.
By comparison, a slight amount of movement is normal. Take note of the movement of the trailer sometime on a calm day after a car hauler type 18 wheeler has passed you, and is out front of you 200 to 400 feet. The air off them is very turbulent, and you will see your trailer doing a little side to side dance.
Sway is like a "worse version" ( greater amplitude, lower frequency at first ) of this dance, that gets progressively wider swings.
Train your eye to see this side to side dance at a glance in the mirror. Understand what it looks like, and think it thru, that if it's getting worse, you are heading into a potential problem.
If it does begin to sway, steady throttle at first, coupled with a "light application" of trailer brakes manually at the controller, followed by easing off the gas will bring it back straight.
That's my experience.
