Some dude on the Nat'l forum gained an extra 8 hp or something close to that with an electric fan (at the rear wheel, dyno'd). I was running a permacool pancake fan in my 3.4L but had too many issues with the control unit going on the fritz (water was dripping into it... bad placement and rubber boot design... some electrical tape fixed that issue) and had the pin that holds the motor to the fan magically disappeared making the fan basically slip on the motor. Glad I was in town and not up in the hills. Regardless, I went back to the mechanical fan for reliability purposes. Also, there's not an easy way to hook up a water temp thermostat in the 3.4L so you end up having to use a radiator fin probe which is ok but not ideal.
If you install an electric fan, make sure to bring your mechanical fan along for the ride if you go anywhere far or go wheeling. Better safe than sorry!!!
Also, don't forget that the stock fan has a built in thermostat that reduces the spinning of the stock fan as the engine warms up.
No Obstacles, Only Challenges.
My Rig: 2017 Tacoma TRD Pro Storm Trooper