The very first thing you should do is install headlight relays. I run a #8 wire straight from the alternator output to a Buss brand fuse block mounted on the power steering reservoir bracket. The relays are mounted both on the inside of the left front fender and in front of the air cleaner on my turbo car.
I use four relays total for the headlights, and one for the fog lights.




Go to this site for more information.

I have seen as much as 2.5 volts lost in the stock headlight wiring system on one car. Make sure your grounds are good, too.

If you want to check the voltage loss, use a digital voltmeter to test between the alternator output and the headlights in both high and low beam. Since power=V²/R, a little change in the voltage to the headlights makes a big difference in light output.

If that fails, there are higher wattage lamps available, go to Dan Stern's web site for one place to buy them.
--
john