If you manifold is cracked it could melt the plug boot like that.
Good Point didn't think about that. Start your engine with the hood open and gently move the throttle if you hear a ticking you probably do have a cracked manifold or loose manifold. Check the bolts and inspect for cracks.
1999 GTPHP Tuned, Ported SC/TB, 42#'s, SSAC's, ZZP Modded 1.9's/LS6 Springs/Manley's, TransGo Shift Kit, Poly Uppers, KYB GR2's/Springtech's. - 231k and traded it in. - Gone 2000 GTP: XP, P&P'd Heads, N*\Lq4 MAF, GenV, 42#'s, PRJ Rails\FPR, Racetronix, TEP w/ 3.29 Gears, 300m, 7/8" chain, SSAC's. - Collecting dust in my garage.