Really late to the thread! Congrats! If you have any tech questions Lmk. Did you join the SIG mailing list yet? A great group of guys very passionate and not Pretentious at all.
S14 exhaust is specific to the m3 afaik. I recently put a used oem supplier mid and muffler on fitment was perfect and looks great. You've probably noticed that a lot of parts are nla by bmw..Much more quiet than the supersprint rear and vsr catted center I had on before.
I just replaced the master cylinder tonight, pedal feels incredible, I really love driving this car.