You could get axelback exhaust. I have Flowmaster American Thunder. Pretty aggressive sounding but still doesn't do the big V8 sound.
https://www.camaro6.com/forums/showp...&postcount=122
Keep in mind the mustang is doing a cold startup. On cold startup mine is loud and sounds like that too then quiets down. I'd be curious what that mustang sounds like on a normal startup and normal drive conditions.