owner's manual says replacing with Leds could cause electrical system issues. Why? and what? I've replaced my Tacoma, highlander and Nismo with Leds and no issues.

 

The computer assumes that the headlamps consume a certain amount of power (about 40W each give or take). This is factored into things like charging system mode.
LED's do not behave as expected.

The vehicle was designed for halogens, which are a simple resistive load.
LED's are not. They have power supplies with inductive characteristics, inrush currents, and switching frequencies which can interfere with electronics.

The warning is particularly true for cheap , poorly designed, budget market LED's that people love to install.

GE and Philips long life halogen headlamps are excellent. Really happy with them.

 

Ok thanks. I'm getting a 32" light bar for front mount. LED independent switch, so not tied into express wiring.