77 grand prix test pipe
 

Does anybody make a cat converter bypass pipe?

EPA would go after anyone who did. Cats are still covered under federal law (clean air act). Better off making your own, for test purposes of course.

My 77 lemans no longer has a cat. And has a sweet dual exhaust. I didn't even have to change the crossmember.

That was helpful

I remember that right after catalytic converters started appearing in 1975, you could go to the local auto parts store and buy a test pipe and a slip-on plastic nozzle that went on the spout of the fuel handle. This was the easiest way to get leaded gas into your tank without tearing up the restrictor in the filler neck. How do I know this? It's exactly what I did with my brand-new 1976 TA. If I recall correctly, the payments on that car were about $200 a month.

Worked at a Champion Auto store from about 80 to 83. We sold a lot of Test Tubes.