I hate to always bring up the AIC or AIC chip in the PCM, but I will do it again.

And it is not odd for a poorly running 496 to have very high IAC - PWM percentages. Actually a poorly maintained 496 engine this is not uncommon. 200 - 496's per year back in my day to have seen almost every darn thing happen with them. Just saying. the higher the PWM of the IAC percentage the harder that IAC is working and the hotter it will get. FYI. It might have sucked / injested the IAC muffler Not uncommon at all.