Great
guide and photos. I followed it on my mk2 Cupra and was exactly as described. Only difference, i used the Dimming light switch (grey wire) rather than fuse box for the power so that my gauge lights up only when my lights are On (this works only for mechanical boost gauge/without the sensor

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Important Note: For those who use a mechanical gauge the 1mm vacuum nipple should be used (the small one from Boost gauge fitting kit), if you use the 3mm that i tried will probably get noise on the gauge. Responsiveness is good was not greatly affected. For those that do not used the Boost gauge fitting kit they will need a restrictor of 1mm diameter.