Truck dies after being on about 20 seconds. Rpm drops and it just dies. After looking under the hood I hear a slight whistling sound which leads me to a possible vacuum leak. My main ? Is where are all the vacuum lines to check ?

 

I'd wager you DO have a vacuum leak. Yeah finding a good vacuum connection is not easy on the newer motors. You can adapt the power brake hose to work however. You can spray some kind of liquid like WD-40 on the manifold, or some Naptha cleaning solvent, since I am not going to recommend using gasoline, although diesel fuel would work with less chance of a fire. If it changes the RPM's at all, you have a leak.