I found this video of the 206 GTi's intake and exhaust system. The centre muffler is at 2:07.
But the centre muffler in my 206 GTi isn't an oval shape. It looks like 2 of these connected together:
So the question is, is my exhaust a popular full system, or has it been botched together before I bought my car? My car's always been a bit loud, but I've always assumed that's what a 206 GTi sounds like. I've never heard another one in real life before.