The NMRA Technical Committee has made changes to the True Street class rule set. Specifically the committee has changed the Exhaust rule to: EXHAUST SYSTEM Any Exhaust exit location permitted. Exhaust system with mufflers required. On Turbo applications the Turbo acts as a muffler. Updated 2020 NMRA Rules can be found here: https://www.nmradigital.com/2020-event-info/class-rules-payouts/