I'm adding a set of cibie headlights to my Toyota MR2 as well as a new wiring harness. I'm curious if the wiring harness will increase the output of a 65/55w bulb or if it's only to run a higher wattage bulb. Thanks!
There is no way of increasing the output of bulbs by changing a harness - the best result you can hope for is that it will reduce the voltage drop due to conductor resistance. On the other hand, standard harnesses are designed to keep the voltage drop within acceptable limits, thus preserving the light output of headlight bulbs. In principle, the heavier the wire gage, the shorter the wire, the lower the conductor resistance and the more volts getting to the bulbs. More volts result in more A (amps) which make the fillaments glow. More amps provide whiter light.