Exhaust System Backpressure (Using Pressure Gauge)
Remove Oxygen Sensor (O2S) or air injection check valve (if equipped). Connect a 0-5 psi pressure gauge and run engine at 2500 RPM. If exhaust system backpressure is greater than 1 3/4 - 2 psi (.12-.14 kg/cm2 ), exhaust system or catalytic converter is plugged.