Regarding the newer coolant system, I was able to finally find some information from our forums. So it looks like other people have noticed it 2012 coolant system revision. Here's the link:
2012 Coolant Overflow Bottle Has Two Caps?
In terms of assessing the status of coolant system, I used a block test kit to eliminate any gasket issues and a pressure test kit to check leaks. Essentially, the tests were negative. I've also removed the bumper to check if there's anything blocking airflow such as debris and found a little flat piece of tree/wood inside in the bottom corner of the bumper but not blocking the radiator. Used some air from a compressor tank to clean the radiator, oil cooler, and intercooler. Lower radiator hose seems hot so I don't think the thermostat is faulty but could be the radiator fan blowing hot air on it. So, it looks like the gurgling is indeed coolant boiling from the turbos.
I still need to look into the fan settings via EcuTek tune or consider upgrading to aftermarket.
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