A few weeks ago, I got an "emissions system service required" message and warning light. Examining with an OBD-II reader, I can see a p1132 trouble code. This is an O2 sensor not switching (stuck rich). With the same OBDII reader, I can see that the O2 sensor output does switch most of the time, so I don't think the problem is with the O2 sensor.
What I think is happening is that there is a vacuum leak, that has caused the ECU to en-richen the mixture, then when the boost pressure rises, the leak causes air to leak out and the mixture to become too rich, triggering the fault.
Does anyone know where these engines usually develop leaks on their inlet side, or has anyone else had this fault code and found it to be something else?
-- Rich