When you say you cleaned the ports did you clean all the passages in the cylinder heads? What I have seen is the passages through the cylinder heads get stopped up and don't allow the air to be injected into the exhaust flow as designed. It usually requires cylinder head removal and sending them to a machine shop to be cleaned via long drill bits and solvent soaking tanks.

Like the previous post says though is you need to be able to monitor front O2 sensor values with the system operating and the values should drop quickly when the pump comes on.

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Mercedes Benz Master Tech - Retired