Vacuum advance for distributor?

I recently purchased a 1996 Metro with the 1.0 and 5spd.
I don't know if the engine is original.
My distributor cap has a provision for a vacuum line, but there are no unused lines that I can find.

Correction, on the center of the firewall there is a bracket with three hard lines in it, the center vacuum line is open on both ends.

My car takes what I think is a long time to idle down to it's proper rpm.
New plugs, wires, cap, rotor, injector, fuel filter and front O2 sensor.
Timing was bumped from 4º to 8º.
Compression is 215/255 210/246 209/245 indicating to me that my rings might be getting weak and/or possible HG leak?

MPG is in the 32-39 range with no change since the addition of the new parts.
No Codes.

if your talking about the cap itself it is just a vent hole. not supposed to have a line going to it. in 96 your car did not have vacuum advance. the spark advance is controlled by the computer. if the body of the distributor itself has a round can with vacuum ports then its the wrong one and should be changed

Thank you.:cheers: