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Absolutely no need to remove or loosen a runner to remove the plenum. However, I do remove the TB and tail piece.
If it refuses attempts, smack it front & rear topside with a rubber hammer to loosen the upper gaskets. Then it should just slide right up and out.
Upon reassembly, I strongly suggest you finger start all Torx bolts to prevent cross threading. Since the runners are offset, it may be necessary to tug on one side after getting the bolts started in the other side.