xbox gave a very thorough answer, though let me clarify that you don't need to convert to a tsi if you want a turbo. You can add a turbo to your esi. Since you are going to rebuild the engine anyway (I'm assuming) you can plan on a setup that is turbo-friendly.

It will cost money, and you might just as well buy a turbo 2g off craigslist for the same amount of money. It's up to you. Since you are starting out with an essentially free car, I suggest you make it a project and spend a couple weeks reading everything you can on this forum before spending a cent.

2gnt: '99 RS-T, killed by a toyota, pending rebuild...
Daily: Volt
Daily #2: '99 EVG ebike- STOLEN by PEDRO