Same smell on my new Boss, not clutch, not brakes, not rich exhaust...smells like burning plastic. Hopefully it's not a problem.

 

That's not many miles. The engines and exhaust systems come coated with a rust preventative that burns off in time. It may take a while. A lot more flow and heat is generated through your exhaust when you're getting on it. I know that smell. Cross between oil and plastic. When I worked at the dealership, some of them looked like they were on fire from that stuff burning off when they just get delivered.