You can try editing your visualsettings.dat file in your update.rpf/common/data, code snippet below.
As far as ELS controlling the emissive brightness or corona flare of the original headlight values that's not a thing, so unless your talking about the flashing of the coronas that ELS creates.
car.headlight.day.emissive.on 180.00
car.headlight.night.emissive.on 105.00
car.headlight.day.emissive.off 0.000
car.headlight.night.emissive.off 0.000