1997 Blazer with 250 Amp Alternator - 2 Gauge OFC Big 3 upgrade + Additional Ground for battery

I have currently been dealing with an issue I've been unable to solve.

First off, my dash voltage seems to be very inaccurate, showing 10-11V when meter test at 13-14v

I'm running approx 3200 watts of stereo equipment (measured at approx 60-100 amp pulls when at max) with a 250 amp alternator, However I am not convinced the alternator is working fully (brand new but possibly defective)

Music doesn't begin to drop voltage until it pulls a large amount of amps, 60-100 amps will drop my voltage to 13.4 or so (tested with fluke meter) , however I get pretty noticeable light dimming and dash light dims.

However, when using stock instruments such as AC, Windows, or even my brakes, I get a noticable drop more than my 60 amp pulls from stereo, This DOES occur without music running, only one instrument at a time dims my lights to nearly 50%.

I am curious if could be anything other than simply a bad ground.

Perhaps a specific fuse link or built in module that is common between these stock instruments.


Edit-- My voltage does seem to return to normal after 2-3 seconds , as though my alternator is simply slow to respond to increased loads.