I also didnt know that the Feds wont allow a cat replacement if the old one isnt defective.
1. The vehicle is missing a converter
2. A state or local inspection program has determined that the existing converter needs replacement
3. Vehicles manufactured prior to 1996 must have more than 50,000 miles, and a legitimate need for replacement must be established and documented
4. In cases of OBD Il-equipped vehicles (1996 and later), the O.E. manufacturer's 8-year/80,000-mile warranty must have expired and a legitimate need for replacement must be established and documented.
Please note that Federal law prohibits removal or replacement of a properly functioning O.E. converter.
When replacement of the converter is appropriate (as outlined above), the E.P.A. further requires that:
1. It be installed in the same location as the original
2. It be the same type as the original (i.e., two-way, three-way, three-way plus air/three-way plus oxidation)
3. It be the proper model for the vehicle application as determined and specified by the manufacturer
4. It be properly connected to any existing air injection components on the vehicle
5. It be installed with any other required converter for a particular application
6. It be accompanied by a warranty information card to be completed by the installer.
(if you need a reason, get it hot and hit it with a hammer) dropping my vette's hot cat on speed bump did the trick for me, too bad i didn't want it broken.
lots of people replace them with other than stock and few get in trouble for having a slightly different setup, for my vette i'm going from 3 cats to 1 when i replace the Y pipe just because new ones are better than they were in 85 and one can do the job of the three 23 year old ones, if it passes and it's present i don't think you'll get too much hassle over it