Had to replace the plastic wire loom today as the old original loom was disintegrating, leaving partially 3 exposed wires.
GM used some sort of heat reflective tape, that is also falling apart, can anyone recommend a tape I can use to wrap the whole loom with?

Hardware store...'heat shield aluminum tape'.

Is it just holding the wire loom shut, or does it actually wrap the loom as aheat shield?

Randall I don't know if it was just to keep it shut or to act as a shield. The material seemed to look like a aluminum exterior or possibly a shield.
Considering this extreme high temp area, I thought adding some heat shield aluminum tape as Mike mentioned may be beneficial. (Thanks Mike)
Gm had wrapped the plastic tubing with the wires inside, a bit further down than shown in the photo