A couple things are making me think that I might have a bad cat. First off yesterday i stopped the car and got out while it was still running and exhaust smoke was coming out under the front right wheel well. Also i have heard a strange rattle at various speeds. It sounds like it is coming from from the front right side of the car. It will seem to stop for a little bit when the car shifts gears. For instance when going from overdrive to overdrive off, I live in the steep mountians of WV, it will kick on, and then kick off when i kick the overdrive back on. Or it will happen just as the car shifts up from zero. SO i'm thinking that maybe the rattle is coming from the cat since i heard someone say it will start rattling when it goes bad. It looks fine from the outside, but i just did a quick look as the ground was pretty wet. So what do you think could it possibably be a bad cat? Is there a good way to check it? Thanks