Dimming lights sounds like an interesting phenomenon. Here's my take on flickering lights:

First, it helps to know that the current output of an alternator is low at low RPMs, and increases as the RPMs increase.

Second, it seems to be widely accepted by the automotive industry to design automobiles with charge systems that cannot provide the current needed under worse case load (while the car is idling and everything is turned on and at maximum).
This is deemed acceptable because the RPMs are at idle for low time periods, and the battery has sufficient storage capacity to supply the missing current required by the automobile during the idling period.
The current taken from the battery during idling is restored when the RPMs increase during normal driving.

The capacity of a battery, compared to the capacity of an aftermarket add-on capacitor, is on the order of 1000X greater. So, IMHO, adding the aftermarket capacitor does indeed have an effect, it's equivalent to adding an additional 1/1000 of a battery to the automobile.

Flickering lights would be noticeable if there were, effectively, no battery in the system and the system were under heavy load. But, I assume, Spensley, that your car did have a good working battery at the time you added the capacitor. So I'm not sure why you feel the flickering light problem went away when you added the capacitor.

Danimal, I want to say something here, and I'm not attacking anyone's intelligence level.

I have been working in a Research & Development department all my carrier as an electrical engineer. This experience has taught me that in order to determine the effects of a change one has to follow a specific change method. This is not happening here, nor should it in all cases. This forum has members from all areas of expertise.

Maybe engineers really are just a$$holes that don't really understand the NORMAL guy (or Crossfiregal). If my style of being direct is offensive to anyone, and I mean anyone, on this forum then please speak up, and I'll take it somewhere else.