I bought a cat back Magnex for my 182 and i too am quite dissapointed with the fit, I am on my second system due to the tailpipes not lining up correctly in the bumper cut outs, also the left hand tail pipe seems to be longer than the right! the sound is similar to the standard one at low revs and then seems to come alive as you nail it.
At the moment i am on first name terms with Magnex in trying to sort it out, but they have admitted that i am not the first 182 owner to complain on the fitment,,,,the saga goes on