I don't think it is neccessary on a manual without A/C, and I removed mine as the engine came from an automatic and my car is standard, without A/C. But if you use the A/C the additional load at idle will cause the idle speed to drop, loading the engine and likely raising eng. temps which in hot climates could be significant. From what I've seen written, the original A/C compressors aren't as efficient as more modern ones and will load the engine more. Some folks have managed to adapt more recent YORK compressors, but I'm sure they still use the CSS to keep idle speed constant. Hope that helps
Richard V