This question pertains to the Ford V10 Triton engine in a 2007 class C motorhome. After getting a smog check, the AC switches over from the front vents to the defrost vents upon hard(er) acceleration. Switches back when I let off the gas. I've read the forum posts regarding the relatively common issue due to a bad check valve, but it just seemed suspicious right after taking to a shop for a smog check. I noticed what looks like it might an open vacuum port as shown in the picture below. It looks like it is on the valve cover on the left side. For reference, the large tube in the foreground to the left is the oil filler line. Does anyone know what this is, and should something be connected to it? Thanks!