Welcome!
Gurgling could be as simple as a bad radiator cap. It's not letting the system pressurize properly and the coolant is boiling. I have had this before.
The head gaskets are pretty good on the B6 engine, not usually a problem. There is a caveat to this, if a previous owner overheated the engine severely, it can cause the HG to fail. Say, by driving too long on a broken water pump/alternator belt (a common enough problem)
I'd check the system for leaks, replace the radiator cap with a new one (cheap) maybe pull the plugs to inspect, and go from there with troubleshooting.
There's a few tiny coolant lines that can cause issues. To & from the idle valve mounted to the intake manifold, runs thru the throttle body then to the bypass pipe around the engine block. Also a tiny 90° line running from the t-stat area on the head to the bypass line. And the turbo coolant lines.
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