ISIRI 4243 is a standard published by the Institute of Standards and Industrial Research of Iran (ISIRI) based on Directive 70/157/EEC. It defines "permissible sound level and the exhaust system of motor vehicles".
The first edition was published in 2002 and was later amended and published in 2010 based on Directive 2007/34/EC.
References
ISIRI 4243 Wikipedia(Text) CC BY-SA