First off, what modulator are you using?
I have the SDC that can be used with Hi beam, low beam and turned off. That unit pulls through the leftside (yes, you have to use the leftside) headlight connector. So now you are powering both headlights through one circuit. Because it draws more power now, the headlights were dim at best! Swapping over to LEDs are a different story, although NOT approved for LEDs, the SDC unit works great with them, since the LEDs aren't pulling as much power through. But the problem with LEDs and this modulator, is that it flashes, instead of modulates.:duck:
There are plenty of other modulators out there. The one I first started with (Comagination), you had to setup your headlights off of a different power source, like a bluesea fuseblock and relay. It only modulated on high beam, and you couldn't shut it off! I'm not sure how it would work with LEDs.