If it is going to leak, it will most likely hunt for a solid RPM @ idle as well. A Tial with a proper spring is not going to leak under any circumstance either since it will have positive manifold pressure (that is equal) pushing from both the vaccum hose side and the diaphragm side. Once a Tial has the proper spring, it will never leak due to its design. Everyone has the HKS, my last and next SR will have a Tial. Redneck engineered in the US of A.