Have you changed any of the settings in nvidia control panel? Make sure they are at default until you get it figured out. Also try flipping the cards temporarily, move top to bottom and bottom to top positions. In sli the top card is worked harder then the bottom card usually. If you flip them and the problem goes away it would indicate which card is acting up on ya. But it really sounds like a power supply or nvlink problem. Are you using a UPS? If so try plugging things in directly to an outlet and not the UPS. 

I have a 1300 G2 in it now. It's only a few months old. I have also plugged both cards into a separate 1600 P2 by themselves and still has the same problem. 

I have not! But this is also on my list of ideas. Granted it's a $90 idea. So I am trying to rule out other options. 

I have rotated cards. Didn't fix the problem. 

All that's left to do is to re install windows fresh.

Also are you installing the nvidia drivers with both cards installed at once?

I remember back when it was a pain when I'd just try adding the 2nd card afterwards.

Rolling back to a different date is always a last resort and usually one will need to reinstall windows as crap will be messed up.

Fresh Windows is another step I need to do. That will be next a suppose. But all setting are currently default. Ordered a new Link as well. 

I have some Fire Strike and Heaven Test using HWinFO64. Can you look at the results and see if you see anything? I don't know how to make heads or tails of the data. 
 
 

 
Here is a Link to three runs I had done back to back using Heaven. All 3 froze at the same spot.
https://drive.google.com/...46qKo1o4PbajXsxCDgs-Il
 
 
 
 
 
Here is a Fire Strike run in SLI both cards that froze
https://drive.google.com/open?id=1kw1K9OUbsYU1FzVyWJBWfCUv9-b6jC8L

 
 
 
 
 
Here are runs done on each individual card in Fire Strike. SLI Disabled and one card unplugged and disconnected. Both the runs made it the whole way through the test. 
   This is card one: https://drive.google.com/...13WQTciyZ-1TtzCIp2tsr4
 
    This is card two: https://drive.google.com/...x4dc3WR3yFxN0k1P10jUbm

So I am having Benchmark problems running my RTX 2080 TI Black cards in SLI. It would seem anytime my cards are under stress they crash (Using Fire Strike and Heaven) the cards get to about 63 to 70 degrees and crash the program. I have went through every trouble shooting option I could find in the internet. It's not PSU, RAM, SLI Link, Software, Windows, Bios, Driver, etc...
 
The PC is extremely cool. Its a nice liquid cooled PC.       THE PC IS NOT OVERCLOCKED, it is running stock settings. 
 
Running one GPU I have no issues with any benchmarks. But in SLI it freezes the benchmark every time, about the same temp in the same place. 
 
I'm using two EK water blocks. Not the EVGA water blocks. I noticed the EVGA water blocks plug into the fan connector on the GPU. The water blocks from EK do not plug into the fan port on the GPU. 
 
Basically I'm wondering if the freezing is because the GPUs are trying to run a fan and because none are connected that there is a safety function in the card that shuts it down. Is this possible? Is not having a fan plugged into the port of the EK water block causing the crashes in benchmark programs stressing the GPU? 

mikeaudi21
So I am having Benchmark problems running my RTX 2080 TI Black cards in SLI. It would seem anytime my cards are under stress they crash (Using Fire Strike and Heaven) the cards get to about 63 to 70 degrees and crash the program. I have went through every trouble shooting option I could find in the internet. It's not PSU, RAM, SLI Link, Software, Windows, Bios, Driver, etc...
 
The PC is extremely cool. Its a nice liquid cooled PC.       THE PC IS NOT OVERCLOCKED, it is running stock settings. 
 
Running one GPU I have no issues with any benchmarks. But in SLI it freezes the benchmark every time, about the same temp in the same place. 
 
I'm using two EK water blocks. Not the EVGA water blocks. I noticed the EVGA water blocks plug into the fan connector on the GPU. The water blocks from EK do not plug into the fan port on the GPU. 
 
Basically I'm wondering if the freezing is because the GPUs are trying to run a fan and because none are connected that there is a safety function in the card that shuts it down. Is this possible? Is not having a fan plugged into the port of the EK water block causing the crashes in benchmark programs stressing the GPU? 

That does not seem like a reason they should be shutting down, how big of a power supply are you using? 

The cards get to 60-70c with water blocks? Seems really high temps for water.