I remember being 19 and getting a car, not an STI but getting the excitement of the car I was going to get and then it sold and I had the lost excitement, that is what you are feeling now realizing you got screwed over. You are not seeing straight, you have the oppurtunity to take it back and get a refund, yet you foolishly choose to keep it. I just had an engine rebuild you are looking at about $5,000 and if your block goes as well, add another $2,000 to that. So rather than spending almost $7,000 ON TOP of what you paid for the car, why not take it back and get something that requires little to no work and save money?
You should of spent a good 3 months on here reading and asking questions before buying a car you know nothing about. As mentioned before you were a salesman wet dream. It is very obvious you are not taking our advice and we look forward to your upcoming, "my engine is making funny sounds" thread. Merry Christmas.