head lights pulse after bypassing my bulkhead

A bad diode or two in the alternator can result in flicker that varies with RPM.

An alternator has three phases that generate sine waves that are 120 degrees apart. Six diodes are used to flip negative portions, and conduct the positive sections to make a slightly pulsating supply. The pulsating ripple is filtered by the battery. The regulator controls the field to regulate the alternator output. A loss of a diode results in dips, missing gaps in generation of voltage. The regulator tries to adjust, seeing the dip, it increases the voltage, but because of delay, it increases as the dip passes. The voltage then peaks too high, and repeats ... resulting in flicker that varies with RPM.

The system is now more tightly coupled, by reducing the resistance. Resistance helped filter the ripple. The bypass made apparent, the diode problem.

The main cause of diode failure is a short on the alternator terminal with engine running, or jumping and starting another car with the engine running.

With all that said, a poor ground at the regulator can also result in flicker that varies with vibration.