Oh one possible bad thing. About 7years ago I lost 1/2 my hearing, and cant hear shi+ and am tone deaf. This was a stripped out na 240. I repaced the cat with a strait pipe cat delete running a Greddy sp exhaust with a seconday muffler. The car ran a little rich from the get go, and when I would downshift it would back fire, lighting up the street signs behind me. Since the excess gas fumes were not burned through the cat, it would fill up in the exhaust then ignigte and shoot flames out the exhaust. Everyonce in a while it would be uncomfortingly loud, sounding like a shotgun blast. So one day, I pulled into my neighbore hood, down shifted for a turn and it exploded. In the stripped out car it was as if I ran over a land mine. It was not just loud, it was pain. As if my ears were bleeding. The secondary muffler exploaded, wrapping the steel shell of it around its self. It was like a big pipe bomb. I could not hear anything for the rest of the day not to mention a head ache from hell. The following day I could hear a little better. By the 3rd day I got about half my hearing back. It scarred the crap out of me because I didnt want to be permenently deaf, but either way, now I have to use my hand as like a cone on my ears directed to someone talking to me half the time. Long story short, thats probably the worst thing that could happen with out a cat. Despite that, I still dont run a cat, but I also make sure Im not running rich.