There is some terrible reading comprehension in this thread, the guy has a DC5. 45SET knows the score though. There is no test pipe or flanged cat that can be removed when running a Toda header on a DC5 without modification, the header bolts straight to the 'cat back' exhaust.

I would get the Toda header cut and and a good quality high flow cat welded in with a donut gasketed flex joint with spring bolts. It is important to retain some flexibility in the header otherwise it can crack. Modifying the header will give you the best resale value of both header and exhaust since most people in Australia will want to run a cat and won't already have one welded into the cat back.