I am looking to fit the 200 cell sports cat that I've seen on courtenay's wedbsite, and also drilling out the precat at the same time.

I have a 2.2 sri, and currently have derestricted the air box, panel filter, and vec pipe. It also has a powerflow cat back exhaust.

What is the advantage of buying a downpipe with the precat already removed, on courtenay's site they are selling the precat downpipe and sports cat for £615. Where as a sports cat is £245, and drilling out my precat is free.....am I missing something?????