idle bad on 1999 Mazda 626

advance auto told me a vacum leak but today i check under my car all over cudin feel no air or leaks idk were it cud be but the hissin really loud it lik comen frm the left side of the intake manfold but idk wat to do or weat is

1 answer
Look at you intake air boot that goes to the Mass Air Flow Sensor. These often split open. Also check your PCV hoses. ( large hose that comes off the valve cover )