The 1/8" NPT auxilary port can be used for monitoring fuel pressure, temperature, etc. The Radium fuel pressure gauge is commonly used. An included preimpregnated PTFE plug can be used if this port is not needed.
Radium Engineering Fuel Pressure Regulator with 4 Bar Bosch Regulator 20-0010-01
Radium Engineering Fuel Pressure Regulator Housing Body Only (20-0014)
Radium DMR-RA Direct Mount Fuel Pressure Regulator -8 AN ORB Black 20-1623-00
Radium FPRD-RA Fuel Pressure Regulator Damper 10AN In /Out with 6AN 8AN Fittings
Radium RA-Series FPR Fuel Pressure Regulator Kit for Subaru STI 08-21 EJ257
Radium 20-0014 Fuel Pressure Regulator with No Top
