That's for the cis injector air shrouding. Maybe the vacuum diagram on the hood will show where it goes. Or block it off. Assuming someone didn't rig the system up incorrectly, you'll probably have a stray hose somewhere in the area.
As someone above mentioned -- the "other" end of the hose should have connected to the air intake boot. Someone may have plugged that end or even replaced the boot. The air from the hose kept the injectors cooler and helped with atomization of the fuel. There is an "O" ring gasket under the barb on the head that will sometimes leak and cause issues. Even more likely though -- Some one could have even replaced the head along the way and "added" the connection with the new head. So it wouldn't surprise me if there was no place on the air intake boot for the hose to connect. Cabbies remained MK1s longer than Golfs, Jettas and other models. Some of the MK2 heads (like the ones found on RD engines with the CIS-E injection system) had bigger valves than MK1s so that would have been a good reason to switch to that head if a rebuilt head was needed. FR
To my knowledge, VW went to air shrouded injectors starting in 84 for the last year of the other A1's. Or was that only for the gti?
Either way, I checked the 86 cabby and it does use air shrouded injectors, so most likely it is stock.
An HT or RD head would have been nice, but I went with a digifant head when I did the swap. No air shroud for me got some nice injector lean going on
I really suck at smog.
I read somewhere, sometime ago that the air shroud was for idle emissions, I think it helped with fuel atomization at low engine speeds (idle). I have that port on my head and when it was on CIS, I had it plugged and left it that way when I went MS. Never had any problems passing smog test with either fuel system.
Thanks i'll double check the intake boot, but I think i'll just cap it off and see how that turns out. Could that be the reason my car is stuttering before the engine gets up to temp? I was thinking maybe the coolant temp sensor but maybe I am over thinking and should start smaller.