brake servo valve pipe location?

hi after giving my gti a service ive noticed that the brake servo pipe with the valve has a broken nipple.i know this is common for them to break as ive repaired one already.since ive owned the car its only had one pipe that goes to the inlet manifold.the other nipple if i block it with my finger the car drops revs and doesnt sound right.i thought that the spare nipple was to connect a pipe to the distributer vacuum.? i have the mfa pipe that comes out the bulkhead that attaches to the distributer via a inline switch with a plug attached.i thought id take this pipe off to see if air is coming out and there is air.i cant get my head round this .any help would be appreciated 

One of them goes to the Vacuum servo ports on the a/c controls if you have a/c.

i dont have a/c its a 83 1.8 dx engine.i cant understand why air is coming from the mfa pipe at the bulkhead which leads to the vacuum on the distributer.its always been like this since owning it 16 years.i noticed some cars have a green cap on one of the nipples.if i block off my one the car runs awful.im just curious as to how this works thanks.

maybe at one time there was a pipe coming off the valve that went to the distributer and had a t piece attached so one end went to the distributer and the other attached to the mfa pipe ?

The vac to the distributor should come off the back of the throttle body via the inline switch. The vac to MFA should come off the brake servo take off, and the remaining take off should be blanked (which is why they originally had the green cap). Connecting the MFA to the distributor will mean you have no vac advance, and it means you have unmetered air entering through the throttle body and the nipple on the servo take off. So, whilst it runs, it's not running as it should. The mixture will have been adjusted to blalnce out the vacuum leak.

thanks for the info.if i put a t piece in between the pipe to the inlet then down to the distributer via the switch do you think this would work? then im left with the mfa pipe that was fitted to the distributer to rerout that somehow.its been like this for years but i did think it didnt seem right.thanks for your help

on the other hand i will take the current pipe from the brake servo valve off from the back off the inlet manifold .move it to the distributer and then a pipe from the vacuum on the dizzy to the nipple then block off the remaining nipple then go about adjusting the mixture. i will try this and see what happens 

followed your advice i rearranged the pipework and wow what a difference its never run as good.thanks for the advise its appreciated 

You are most welcome! And thank you for posting to say it's all working!

thats no problem this is what make owners clubs the best help available, good advise is priceless thanks