shakes at idle
 

hi everyone
2000 alero 2.4 l engine
shakes at idle worse when AC is turned on
i have watched the engine and as soon as the ac engages the shaking occurs.

what we have done
checked all motor mounts (?shop says they are fine)
complete tune up. plugs, wires, coils (shop did the tune up)
new Ignition control module (if anyone needs one i have the old one since it did not fix the issue)
new idle control valve

next to the idle control valve there is a small 90 degree hose which i found has a small vacuum leak but i don't know what this hose is called (does anyone have the name). when i hold my finger over it, the engine picks up a little bit but does not solve the shaking issue.

So looking for the following:

1. identify the name of the small hose (see diagram)
2 assistance with the shaking problems