I don't think you need it if no O2 sensors after it. I would still recommend a tail pipe, here's why. My first Jeep was a CJ8. The exhaust after the muffler fell off. I left it that way, with a half cab, it would pass imspection. Guess where the frame started to rust, yep, right above the end of my exhaust system. TJ's are getting a reputation like CJ's to have frame rust issues, it just seems like it is not taking as long for TJ's to have issues as it did CJ's. All the condensation built up and started sped up the rusting.
A dump will also stir up more dust on a dry trail that a rear exit pipe. The guys behind you might appreciate that also.
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