Replacment springs for TiAL 50mm blow off valves. These springs are available as 7 psi, 9 psi, 11 psi, or 12 psi versions.
Which spring do you need? For engine vacuum readings from: -22 and -23 in/Hg - the 12 Psi spring. -18 and 21 in/Hg - the 11 Psi spring. -14 and -17 in/Hg - the 9 Psi spring. -10 and -13 in/Hg - the 7 Psi spring.