92 740 vacum

My 92 740 2.3l no turbo.There are 3 vacum hoses connected to the intake manifold.one goes to the MAP sensor, the one under it goes to a valve(that I don't know what it is) close to the fire wall...The 3td one...COULD SOMEONE PLEASE LOOK AT YUOR ENGINE AND TELL ME WHERE IT GOES TO???!!!.My engine goes crazy on cold start, and on top of that the "check engine light"came on last night.Please help.Thank you