FlatOut 4: Total Insanity Save Game Location
Windows
Steam:
FlatOut 4: Total Insanity save games installed through Steam can be found on Windows here:
C:\Program Files (x86)\Steam\userdata\[user_id]\402130\remote\
Linux
FlatOut 4: Total Insanity save games can be found on Linux (Proton) here:
~/.steam/steam/userdata/[user_id]/402130