2014 Infiniti Q50s, Voltage Problem

2014 Infiniti Q50s. I have a nice system I put in a while ago, I know the amp draws a lot of currant Taramps MD8000.1 and I havent had any issues, I even put a secondary audio battery in the truck to maintain my voltage. Amp is way more than I need to push two 12"  Pure audio X-12s version 3, only putting 3000 watts to them at 2 ohm. About a week ago my voltage started to drop from 14.4v to a low 13v-12v, i started to try and narrow it down, first disconnected the subs- no change, then disconnected the subwoofer amp- no change,then I took the fuses  out the lines going to the secondary battery- no change. I have a brand new starter battery up front, when i'm on the gas it will charge to 14v or so. When i coast at high speed, volts stay high but, when im on the gas lightly the volts drop to 12.4v or so. At a stop and it depends sometimes i'm at 13.5v sometimes i'm lower, I looked over every fuse going to the alt, ecm, everything and all are good. I read somewhere that If you disconnect the Alt for a bit, it will reset so I tried it and Nada. I had the Alt checked and at the time it checked OK, Big 3 done, all upgrades to grounds done under the hood with 1/0 gauge OFC wire. Block to chassis 1/0, Negative post to Ground 1/0, and Alternator done with 1/0. Even though Alternator is stock 150amp It's still charging when needed so I think it's still good and not the issue IDK,  I am dumbfounded. Right now all aftermarket audio is disconnected and problem persists.

Taramps MD8000.1

2- Pure audio X-12s Ver3

CT Sounds Universal Bass Knob w/digital voltmeter

XS Power D5100

All 1/0 Gauge OFC

2 runs of 1/0 to the amp

2 amp grounds

Big 3

Any comments or help would be helpful, 

Thanks, Mitch

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Old school car audio installer, getting back into it, Newer cars are all electric now!