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My buddy has a 97 f-150 with a 4.6. Lately it's been having some idle and starting issues. When at idle the rpm's tend to surge and after it's at operating temperature, if you kill it, it gets difficult to start back up until it cools off. I'm pretty sure we narrowed down the problem to one of the cats. He said it used to throw a cat code but he never did anything about it. Now the code doesn't come up. However, I thought it would be a good idea to pull the O2 sensors before the cats. If the cats were clogged then the problems should go away since the exhaust isn't fully flowing through them. So we did and the idle and start up issues were gone. That leads me to believe that one of the cats are clogged. Instead of replacing it, would there be any back pressure issues if we removed the cats and made it straight pipe? Or should we just remove two of the cats and leave the other two so that we keep some of the back pressure? It has some tornado thing after the throttle body to increase the intake so I was thinking that maybe that has been causing the cats to go bad since the intake was increased but the out flow was not. Thoughts?
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