The 182 has a completly different exhaust system, the manifold on it is a big old thing that includes the down pipe, it then bolts to the 'straight' cat. The 182 cat is slightly further back and is joined to the rest of the exhaust by a U clamp.
The 172 manifold is joined about halfway down the down pipe to the cat via a sprung gasket join. Look on k-tecs website and compare a 172 decat pipe to a 182 decat pipe.