Si header on my STD hatch

Hi,

Since I am planning on replacing my head gasket in the hatch and I have to remove the header anyways to get to the head I decided to take the very restrictive STD header (with a CAT on it) and replace it with my SI one that I got from the SI engine I had.
Will it bolt right in place of the STD header and connect to the exhaust?

I was planning on buying an aftermarket header but since im low on $ and I removing the header anyways i want to know if its possible to do this. I should get a decent increase in HP right? I have the MPFI swap completed also.

Thanks

it will bolt right up and you will have no cat.

Will it be a lot louder with no cat?
Thanks

Yes, lots louder with no cat. Depending on if you have factory muffler or straight through design style.

Ok, how much HP do you think the STD cat is restricting the car with an MPFI swap?

a lot :)