Unknown capped Vacuum line

[Pete1122]

I have a vacuum line that has a screw in it to cap it off, as seen in the picture it ends near the battery on the rear passenger side. I have tried to trace it back, however it goes behind the engine and disappears under the other lines. I cannot seem to find any missing connections where this would connect to on the passenger side. Any thoughts or help?

1993 Nissan 300zx NA Convertible.

[itsa300zx]

Has your EGR system been eliminated or bypassed? Looks like it might be the case and that line would go to the EGR diaphragm. Your 93 vert doesn't have the older AIV system so can't be that.