This softer spring is supplied standard in all Mach 2 valves that are fully recirculated. It can be fitted to all Respons TMS and Deceptor Pro valves too, but should only be used when the valve is fully recirculated and/or the engine idle vacuum is less than 19"Hg.
If the valve is to be used for atmosphere venting and the engine idle vacuum is over 19"Hg, use the standard spring 6115.
