An aftermarket cat will pass inspection. There is no law which says you need OEM parts.

If you get one installed and get your O2 sensors back on so the check engine light is off and a garage refuses, please report them to the state.

*also, were you to straight pipe until later, your car will not run like shit. It will run a little rich and get a mile or two less a gallon but you will be spewing a lot more emissions into the air.