Is it my alternator? Somewhat odd electrical issue

I recently had a racetronix fuel pump installed with the upgrade wiring harness. It pulls power directly from the alternator (74000 miles) and for some reason, my lighting has been acting up a bit. One odd thing is that when I hit the brakes, the lights will dim on my head unit. Same will happen when I use the turn signals and will dim in sequence with the signal. The harness grounds to the passenger side ground location btw. The volts (on the guage) are always above 13 and look to be around 14 when running during any kind of driving. The car has the factory alternator and 3 month old red top optima battery. Car starts right up and no other issues. Any ideas?

-Brian