Supertech Intake Valves Black Nitride for 6G72 3000GT PIAA AutoMeter’s race proven air core electric Lightweight high grade 6061 AutoMeter’s race proven air core electric tachometers provide quick and accurate readings with a needle so responsive it can go from 0 full scale in 333 milliseconds (1990 1992 1991 1999 3000GT & Stealth VR4 6G72 Twin Turbo Supertech valves are made from one piece of forged stainless steel and go through a special heat treatment process that obtains the right amount of harness for each engine to ensure the ultimate valve for your 6G72 motor keeping good ductility beneath the hard nitrided layer (microhardness is 800HV minimum)