acura rdx warm-up catalytic removal

I’m working on replacing my 2008 Acura Rdx Turobcharger, which requires removal of the Warm-Up Catalytic as well. The WU-Cat is attached to the turbocharger exhaust by 2 bolt + 1 nut. The nut is in an extremely tight spot and all fasteners are supper rusted and they can’t be removed. I have already tried a propane torch and Venom HP induction heat gun to get the bolts bright red, but that has not worked either.
What tools + techniques are required in order to remove rusted bolts?

Any suggestion would be appreciated.

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