Taking off any of the cats, or exhaust manifolds (to be replaced with headers) will cause your check engine light to come on. The manifolds and cats were tuned to your vehicle's engine at the factory. So when messing with the exhaust system in anyway before the cats, will cause the light to come on. When I first got my Ranger I wanted to cut off at least one of my cats. However when I took it to the exhaust company ,that my granddad has been using for years, the exhaust technician said not only would I lose power, he also said I would have to deal with the check engine light coming on too. So from the cat back I put on a delta flow 40 series dual output flowmaster exhaust on my Ranger and am very pleased. I get asked alot on how I got a V6 to sound so good. See a V6 needs backpressure to create low end torque and horsepower. Diesels on the other hand really don't. So with all that said if you want to cut one of the cats off, go ahead it's your truck. But you will need to find a programmer or something to turn off the check engine light for the sensors that may have been lost on that catalytic converter.
