To extract the broken bolt, I used a Snap-On A80A stud remover/installer. Afterward, I chased all the threads with a rethreading kit & thread files. Then all were rinsed with brake cleaner (including inside the heads & the EGR fittings) and coated with nickel anti-seize lube.
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I didn't fix it on this truck, but the evaporator insulation at the L edge of this pic can be replaced with a more-robust modern material, like this:
