I was perplexed by the vacuum gauge. While I had my instrument cluster out for odometer repair, I did notice that the Eco gauge was peged out in the red. I sucked on the nipple on the back of the gauge and the needle went to the middle region. The gauge measures the amount of vacuum available. A gauge pegged out in the red means you are using almost all available vacuum either due to heavy acceleration or due to leaky vacuum hoses somewhere in your system. Mine hangs out around 3/4 most of the time.
1987 190 Euro