For the Cessna 172 airplane models incorporating Lycoming O-320 engines: Modification of the standard exhaust system as documented in Laminar Flow Systems Installation Instructions Document, "Laminar Flow System Extractor Exhaust System" Revision A, dated, November 20, 1998 and Technical Drawing List, Book No. PFS-B-800, dated, November 16, 1998 or per Power Flow Systems, Inc. Installation Instructions Document PFS-0058-00, Rev. A, dated October 5, 2001 and Master Drawing List, Report No. PFS-0032-00, Rev. IR, dated August 10, 2000, or later FAA approved revisions. For the Cessna 172 airplane models incorporating Lycoming O-320 ,O-360 0r IO-360 engines: Modify the standard exhaust system as document in Power Flow Systems, Inc. Installation Instructions Document PFS-13250-00, Rev B, dated, December 9, 2002 and Master Drawing list PFS-13240-00, Rev, IR, dated October 3, 2002. View PDF on drs.faa.gov ↗

The STC PDF is authoritative: installation instructions, ICA requirements and limitations.