So when I'm driving or occasionally in park and idling the voltage will randomly drop from around 14V to around 9V or 10V, sometimes far enough for the battery light to come on and the blower motor/lights to slow down and dim.

It has a new battery, new (refurbished) alternator from Advanced Auto Parts which I have taken back and tested and it tested good. All the connections via the battery and grounds including the engine and chassis are all good. One thing that I suspect could be the voltage regulator in the PCM, I would like to convert it to the older style voltage regulator that's built in to the alternator if anyone could give me any directions on that. Any help would be much appreciated!