A quick question. please answer

[SilverEX]

I know this has been talked about but I can't find exactly what i am looking for in a search. I want to put an SI exhaust on my EX. I know it will fit and I have to take the springs off. I heard that the holes don't line up perfectly. Which holes, the bolt holes or the exhaust pipe hole. I read that I will need an SI exhaust flange, what is that, is it just a donut gasket that goes in between the two pipes? I hope somebody can help me because I can get an SI exhaust for free. Like I said im sure all of this has been talked about but I had no luke finding it. Thanks alot