Hi,
When my 94 C280 suddenly started to idle high (around 1500 rpm) I popped the hood to look around. To the left of the fuel rail and between the two fuel injectors, I discovered what appears to be an open vacuum connector that can accomodate a 1/2" vacuum line. The problem is there is no line hanging loose around the connector. It's possible the previous owner plugged it and what ever he used to do it fell off. Does anyone know what the port connects to?