None of the current RCC plenums have bungs installed for this purpose, and I have never seen Richard do this. Normally we would relocate this sensor, either forward in the ram air tube, or along the inside of the left frame as far back as possible to get it away from any hot air. You might want to try getting it out of the plenum and putting it somewhere else . . . maybe someone else has seen an issue like this and can comment . . .