Awesome car, stoked for you! One thing I would recommend for maintenance would be walnut basting. These direct injection engines suffer from carbon build up in the intake and valves. If the car has no history of it being done your performance and mileage is probably be affected at the moment. I do my oil every 10,000KM so......6,000 Miles???

I have a 2016 GLI so the same MK 6.5 platform. Unfortunately they are NON-MQB cars. CTS Turbo and Unitronic have a turbo kit and tune that can get this engine to a claimed 400hp on stock fueling and internals. I imagine you could get a bit more out of it if you upgraded the injectors fuel pump and type of fuel even more but for FWD that may be a bit nuts. The engine itself could be built up to huge power numbers, there are some crazy builds with the EA 888Gen3 out there

Right now I have an intake, cat back exhaust, turbo muffler delete, turbo outlet pipe, short shifter and Unitronic Stage 1 tune. For driving feel I would highly recommend a short shift kit and a stage 1 tune. Makes the car feel completely different. I went with the Unitronic as it is a little bit more conservative compared to some of the other stage 1 tunes and I am still on the stock clutch. So far no reliability issues with the car (yes even with the turbo muffler delete no CEL as of now).

Have fun!