Higher octane definitely helps resist detonation but I can't see it burning any hotter. According to TH, your exhaust actually gets hotter when you retard the timing too.

Tom

Former owner of '99 CSVT - Silver #222/2760 356/334 wHP/TQ at 10psi on pump gas! See My Mods '05 Volvo S40 Turbo 5 AWD with 6spd, Passion Red '06 Mazda5 Touring, 5spd,MTX, Black