98. Exhaust system back pressure is customarily measured at the discharge of a turbocharger. If the exhaust system back pressure is higher than normal for a given engine load on your salvage tug at the point of measurement, which of the following conditions would most likely account for this?

High exhaust back pressure measured at the turbocharger discharge is most likely caused by a restriction downstream of that point, such as a blocked exhaust silencer/muffler. Restrictions before the turbocharger primarily affect cylinder and manifold pressures, while intake restrictions affect air intake, not exhaust back pressure.