Yeah you didn't have to make a variable for that, you could make the cameras boolean values or just write "camera = 1". Anyway great job with the sounds, actually i already did interior engine sounds once but i had to change the sound files everytime.
#ALAN :
I wonder if you could make it pitch the sound differently, so you wouldn't need extra banks for it, and could do it globally
Probably not possible cause even FH3 uses different sounds for interior and exterior, but who knows ¯\_(ツ)_/¯
