ROUSH 2012 Stage 3 Mustang ROUSH 2012 Stage 3 Mustang. HT: StangNet. StangNet has alerted us to Roush’s official public release concerning its 2010 Stage 3. Supercharged and fine tuned, it sounds like it will be a noteworthy car. Still no side exhaust. But read up, and tell me what you think about it.