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The best way to know for sure is to scan it for faults. Autozone or other large chain parts stores will do this for you for FREE, post them back up in this thread and we can narrow down the causes. A 1.8T can have a number of different things that could cause this, so it's best to know the faults rather than throw expensive parts at it.
When you update this thread it will let me know.
I think you have a couple different issues here- the misfire faults, knock sensor faults, and O2 sensor faults, I think are caused by the main issue, which seems to be two-fold. You have an intake air leak, making the system lean- also a failure in the EVAP system, which leads me to believe that your leak may be the N80 purge valve (do you have problems starting the car after filling up with fuel?)
I would start the car, open the hood, and listen for any hissing air leaks. Start at the rubber "Y" pipe at the end of the valve cover (remove the plastic engine covers) and inspect the PCV system, that rubber Y or the s curved plastic pipe below it, also a couple of hoses right under the intake manifold area.