I know you don't live in the People's Republic of Communistic California... but I had a friend who bought an e46 m3 that the first owner had hollowed out the cats of. Turns out the guy must've used a shady smog place as he smogged it before selling the car... but, after 2 years, my friend had to smog it again and there was NO WAY it was going to pass. He took it to the dealership and the dealership voided the 100k mile warranty on his cats, because they'd been hammered out.
It was a real pain, he had to buy new cats for the car, and even used, they are not cheap. The car got flagged a gross polluter and he had to jump through hoops to sell it, and it showed up on the carfax. He really got hosed. It may not be the case in the rest of the country with easier smog laws, just wanted y'all to understand where I am coming from.