Follow the vacuum tube from the brake booster to below the intake manifold. The line is in 3 pieces, all pieces are hard (silicone ABS type plastic) the middle piece has a slight bend below the intake runner. This is where I located the hole. I believe through rubbing over time the hole caused a vacuum leak to cause a P0171 fault and eventually it became big enough to cause the loss of brake booster efficiency. I replaced the bad section with 15/32 PCV hose and the cost was $2.89, the car is running like a top now with no codes pending after 2 days. It is tough to hear because of the TB being right above this area. Feel the length of the tube (engine off) and if you feel a rough area on the tube it could be rubbing as well. HTH
