Welcome. These diesels are capable of really good mileage with a few basic mods and a patient driver. I am including a shameless plug to direct you to a thread I started after 12 years of hypermiling my TDI. It is a combination of eco-driving tutorial and build thread.
https://ecomodder.com/forum/showthre...sel-38306.html
I got a ScanGuage and blocked the upper grill right after I got the car and have never removed it since. It runs warm enough for the fans to turn on during long climbs in the Rockies but it cools right off at the summit. Also, I removed the muffler early on and replaced it with a straight pipe with a turn down to exit in the factory location. With the turbo and the cat in place it is not loud. It makes a cute little spooling sound when you shut the motor down though.
I experimented with blocking the intercooler grill in winter but decided it was not for me. Nothing to be gained there.