I have been hearing a noise from the engine of my Tahoe for the past week. Sounds like a flat tire hitting the pavement over and over when you're under the hood, and from the inside it almost sounds like a chirping or sipping sound. It sounds like an exhaust leak that is from the intake manifold somewhere. It's coming from the driver-side intake, right below the TB/Intake mating surface. Could be a bad gasket? Anyone?