Metal heat soaks I've seen it, and cools down waaay slower than plastic tubes. I don't care how much coating is on them. But that's just me.
2001 ws6, 40k miles, Ls3 416 stroker, short block built by PER the rest by me. LPE Ls3 heads milled to 12-1 comp, FAST 102, NW 102, kooks 2", dual DMH cutouts, Magnaflow C/B, BTR cam + springs. Full UMI suspension.