Hi everyone, I did try searching before hand but couldn't find what I was looking for.

The issue is when the car has a high load (28+psi). The voltage reading reads 13.8-14.0 while cruising. When the throttle is at 100% and gets high boost, the voltage drops to 12.4 and causes misfires. Obviously, we haven't pushed it that far again because we don't want a blown motor. However, under 20psi, the voltage drop is still there but the car doesn't misfire because the load isn't as much. Car has been turbo'd for almost 2 years but we just started turning it up now so the issue could've always been there, but we're just now noticing it because we are putting more load on the motor.

Precision 6262, w PLM Twinscroll - Car made 563 before turning it up.

Here are the things done to the car that would possibly influence it.
Battery relocated to trunk with 0/1 gauge wire for power cable, ground and power steering.
Hardwired 450 fuel pump with relay
Relocated fuse box to passenger side air bag area (air bag removed) - Done by myself. Wires extended one by one and soldered.
Haltech Elite 1500 ECU - Plug N Play Harness - (Had AEM EMS Series 2 and still had the same issue)
ID2000CC injectors
AGM Battery (Brand new basically)
NEW OEM Coil Packs
OEM Alternator replaced with only 4,000 miles on it (came from a wrecked car)
Power Steering extended wires for relocation (Same gauge as OEM)

Here are the things I've tested to eliminate issues
Tested ground for battery - Reading was 0.1
Tested ground for motor - Reading was 0.00 while car was running (verifies that the motor is properly grounded)
Voltage reading while cranking is 13.8
Haltech remoted in to my car at the shop it's at and they verified everything is setup correctly.

What in the world would cause this guys? I really don't think this car needs 2 batteries. Electrical gremlins are the hardest to find. On a side note, which is power related, my EPS works on and off which could be another issue due to voltage drop. I'm not worried about EPS though. Main reason is finding the issue causing the voltage drop. Pic from data log is attached. Bottom of screen - Red Line is TPS, Blue line is batt.

 

You should measure the voltage at the alternator, use a strong alligator clip or something similar and keep the multimeter in car or where you can monitor it while doing a rip.
If the voltage stays stable then you got a wiring issue, move the alligator clip further away and check again.
I don't see any crazy electrical consumers in your system so the stock alternator should provide enough current.

"Voltage reading while cranking is 13.8"
There is no way you get that high voltage with a normal battery during cranking, make sure you check that again.

 

Let me know when you can bring her over

 

Have you considered a contaminated or old serpentine belt? Maybe auto-tensioners culprit, so slip at high rpm.

 

Measured the voltage at the alternator during a pull and it never dropped below 13.9. Measured at the fuse box during a pull, never below 13.9. After a few pulls, fuse box alternator wire dropped to 13.4 at idle. Changing alternator to fuse box wire to 0 gauge tomorrow to see if that does anything. Also changing out ELD in fuse box.

 

Well guys. It ended up being the OEM alternator cable dropping voltage. The wire was extended during the fuse box relocation and it wasn’t the correct wire. Same gauge as OEM but terrible quality. Replaced with 0 gauge wire and boom. No more drops. Thanks for all of your help!

 

That's great to hear