If when you floored it all the lights came back up to normal brightness, it sounds as simple as the alternator not charging. When you turn the ignition on, does the battery light illuminate?

If it does, then you have another problem, if not, take the small blue wire from the D+ terminal on the alternator and connect it to earth with the ignition on. The battery light should come on. If it does, the diode pack in the alternator has died and the most cost-effective solution would be to replace the alternator. If the light does not come on, either you have a broken wire or the battery light bulb has blown (not uncommon).