My wife bought a 2000 Kia Sportage 2WD 4DR. About 3 weeks ago, she told me the car was acting funny. I drove it and there was a strong sulfurous smell coming from the bottom of the car and its acceleration was significantly decreased. It seemed to me just like the catalytic converter problem I had with an old Monte Carlo. I told her not to worry, I'll fix it. I've looked to replace the Cat, but everyone wants $750 -$900 for a new one. So I've been looking for one used, but noone will sell me one (they say its against the law to sell a used Cat). In the meantime, with her still driving it, things have gone from bad to "I'm going to set this thing of fire and you'll take a cab to work!". Now there's a loud banging from under the valve cover, kindof cyclic (comes and goes every 1-1 1/2 secs.). I've stripped it down to the head, but I've never worked on a DOHC before. If anyone has any advive, I'd be eternally grateful.