I'm wondering, whats the biggest turbo i can put into a 2000 pontiac sunfire with the 2.2l engine? And what kind of modifications will i need to do to get it to fit?

well it all depends.. if you want to run tons of boost or just add a little kick... i think a good turbo would be the t23.. can run lots of boost and wont ruin the motor right away.... you have to get bigger fuel injectors or just get a new fuel management system because you will hit fuel cut right away.... there are tons of options man...

With the turbo you need to remember the price will play a lot into it. I have a 2.4L 2000 sunfire GT, for me it will cost around $5000 (in canada) for an average one. I paid 3000$ for the car, I may as well buy a new car. Just some "food for thought".

It is on you.