Stainless is a very poor metal to use in 'vibratory' applications .... you typically only get 1 million load cycles at greater than 1/3 the ultimate tensile strength ... then FATIGUE becomes a real problem --- 'cracks', and other 'sudden catastrophic failure'.

Worse, fatigue begins from the very start of installation ... and then you have HOT chlorides/sulfides from the exhaust gases penetrating into the microcracks, so you have two failure modes propagating simultaneously.

... the best for exhaust systems still remains to be 'cast iron'.