because it aint quality.
When you turbo a car, you've kicked reliability out of the door.
2.0l was designed to be bulletproof fool.
Get a jetta vr6 or 1.8t if you cant afford insurance for gti.
Expect to refill your gas every week. (40 dollars for me)
What? How isn't that quality? It's a remanufactured BW turbocharger. There is nothing wrong with that snail. $635+ really isn't that "cheap" though. There are better options for the budget build route.
When you throw a hack-job turbo setup together you throw reliability out the window. With a smart setup, good tune, proper monitoring (as easy as a quality wideband... better yet add in a decent knock metering setup) you're set.
However, don't waste your money. You don't have the funds to turbocharge your car, you definitely don't have the money to do it properly, let alone maintain it. In the end you're still running an open-diff'd transaxle with garbage gearing.
Lower it, throw some wheels on it, and keep it maintained. You're young. Save your money, drive it for what it is and when she breaks - fix it. This is the best way to learn, stack some cash in the bank and once it's a bit more viable you can buy something worth sinking money into and making some power.