The Cybertruck Is the Dumbest Thing I've Ever Seen: Elon Musk enters his Caligula era.

[ProfessorGAC]

68. Where Is The Chloride In Space?

Not sure how SpaceX comes into it.
Also, 304 is 304. If the came up with an alloy with unique properties they'd assign a number. There aren't 99 varieties in the 300 Series.
Mufflers are mostly aluminized mild steel. That's because they are cheaper & last longer.
Some are stainless, but they're often epoxy coated. Racing mufflers are often 304 or 321, but longevity isn't a priority for most race cars.
There is nothing speculative about corrosion resistance going on here.
Chloride stress corrosion is a well-understood phenomenon and austenitic stainless steel are highly susceptible to it.