possibly its heating up ur exhaust too much or the heat shields arent blocking the heat from the floor panel, get under ur car next time its hot and see exactly whats really toasty, possibly the cat uve got is too restrictive and is causing things to heat up more than theyu are supposed to or something is lodged or clogged in ur exhaust. a straight smooth flowing exhaust will be hot all the way thru, while a stricted will got hit in certain places.