I've got a 1991 F250 with the 4.9L 6. I originally bought the truck when I lived in California, but now live in Oregon. Its come time for a new cat. Does anyone know if I have to use the California Cat or if it will screw up the computer if I go with a 49-state cat. The 49 state is a few hundred bucks cheaper, at least from magnaflow. Thanks

 

just gut the cat you have now, or replace it with a straight pipe. much cheaper solution. on my 92 there are two cats (well, there used to be). the one downstream (closest to the tail pipe) will not affect the computer if removed because there is no oxygen sensor after it.

 

Octane, I have 2 cats as well. I assumed it was a California thing since the replacement shows two cats for CA and only one for 49-state. Can I gut both cats and still be fine with the O2 sensor and computer?

 

Should be just fine since that third o2 sensor is where the y pipes come together

 

There is no downstream O2 sensors on trucks built before 1996, most 50 state and Canadian trucks have a single upstream while MAF Cali spec trucks have two upstream sensors, but because these are all upstream it really doesn't matter what type and number of cats a truck has as they have no effect on engine operation.