Yes, an electronic flasher is required if you change over to leds on both ends, and in some cases, even if you only do one end. In my case, I did the front first, with hi-wattage halogens in the rears. Std flasher worked fine. But when one of the halogens burned out, and I re-installed the std bulb, they would only flash very slowly. I now have leds both ends and an electronic flasher ($11 at Auto Zone), they work fine now. I also put the same flasher in my beater Blazer (still incandesant for now), it seems more reliable that the old style.
