All good safety points but none of which touch on the reason for the rule change: to keep cars looking like cars and not like diesel trucks. There's no mention of exhaust exiting restrictions in CC or MS in the rule book but there are for ALT and GC (allowed in ALT, not allowed in GC). Seems like instead of a blanket "not allowed" rule for all door slammers, it'd make more sense to establish some guidelines for the classes that don't specifically state one way or the other. Or, just assume that since there's no mention in CC or MS that there's no restriction.
Also, FWIW, I tuned the red Z that I posted pics of. With a nice long standing flame after the end of a WOT dyno pull, there's no sign of any heat damage to the car whatsoever. You guys act like it's pointed at the drivers face or something. The exhaust is directed up and over the top of the car.