Hey so I have an 05 a4 Quatro 6 speed. 140k miles in the k03 went out on me. My financial situation has declined so I couldn't afford a full price turbo so I bought a k04 on ebay for 200 dollars. I don't think that the k04 is boosting enough so I'm getting an electronic boost gauge installed this weekend to monitor it. I also have a CEL for turbocharger under boost condition. I was wondering if someone could answer 3 questions for me

1 what was I thinking buying an eBay turbo?

2 what is the stock target boost for the a4?

3 could the under boost condition CEL be cause by the later spool of the K04?