[lineslinger]

Hi blykins,
Your analysis makes sense to me.
I thought about your post for a bit and a couple of things come to mind.
I am assuming that if you have a fuel pressure regulator you are running an electric fuel pump.
If the voltage output (from whatever source) is not optimal your whole system after the alt. is being starved for power. The fuel pump now has to work even harder to build up enough pressure to deal with the regulator which may be why the performance suffered even more after you put it in. It can't do it, not enough volts for its design.
Without optimal/proper voltage at idle it cannot make the desired fuel delivery, thus you need/tried/considered enriching the idle.
With low voltage the entire ignition system is "starving" for enough juice to create a spark that is big enough and hot enough for its designed delivery, even if your ignition has a capacitor, that "stored" electricity is used up very quickly once you fire the beast up, the combustion within the chamber is not sparking/burning the fuel properly or completely.
When you blip the throttle the fuel pump works harder and the ignition calls for more juice. The low voltage will not allow it to do so, thus, louder FP and brighter ign. light.
One other thing you might consider is before you start doing all the electonic trouble shooting necessary, try changing out the pulley or pulleys and see if the problem still remains, if it goes away thats a pretty good indicator as to whats up.
I think slithering has got it right about the voltage regulator.
Low voltage at the source of electricity is producing a trickle down effect that is affecting efficiency on both sides of the system.
Sorry to be so long winded but I hope this makes sense.
Just some things to think about, good luck.

Mark