I'm currently on the hunt for another 172. I went to see an 02 plate one today and noticed that the exhaust note was a little raspy for standard. When I asked the dealer about it he told me it had a brand new standard system on it, but it had a 4 branch manifold, hence the deeper tone. I've never heard of anyone to do anything than fit a 182 manifold to a 172 before so I'm a bit confused. Has anyone else done this to theirs or heard of anyone who has?