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12. The idle enrichment valve opens the idle circuit to an extra air bleed, leaning the mixture—except when vacuum is applied during warm-up. It could more accurately be described as an enleanment valve. The barrel shaped device is the high altitude compensator. It senses air pressure with a gas filled bellow, opening and closing off an extra air bleed to adjust the main metering circuit. Though it was added as an emission device, the idea of altitude compensations sounds good enough to keep it.