O-ring seal in the charge air cooler coupler

This could be the cause, but I would suggest confirming it first by smoke testing the charge air cooling system.

Basically, there are a number of things that can cause this but if you are checking for a vacuum leak, you are basically doing the same thing but smoke testing the charged air side with the engine off is more definitive.

https://youtu.be/4ktw1X4W_-k

This TSB is telling you the same thing.

However, if you inspect this o ring and it is there and not damaged then it is likely not the issue.

As for replacing it, you just take a small automotive pick or pocket screwdriver and pull it out. There is no repair process for this as it is just a removeable o ring and they didn't list how to replace it.

As for finding it, we are going to have to go to a parts store and match up the o ring to the bulk O-rings that they have.

If they don't have it, then you are going to have to go to a dealer and see if they have an actual part number for it. Otherwise, they should have one in their bulk o-rings for when they need to replace this.