Need Help with a vacuum leak
I recently had my engine idling very hard. After going to advance auto parts (aap) and got my CEL's checked. After I went and consulted a Subaru mechanic I learned that the codes I was getting (PO171 x2) were telling me that I had a vacuum leak, and that it was somwhere between the MAF (which I think is right there on the on the air filter casing, please correct me if im wrong) and the heads... Which leaves a lot of piping. How would I go about checking where it is? I have no idea what to do so any help would be very helpful.