1977 Porsche 911s Targa 3.6 varioram motor running without muffler #2

About VarioRam

VarioRam is a Porsche-patented engine induction system that was first introduced on the 1992 model year 964 Carrera RS motorsport special. It became standard on the 911 series starting from the M64/21 engine on the model year 1996.