[Liam986]

Codes P1125, P1126, P1132, and P1133 indicate that the engine control module (DME) in your Porsche 986 is at its enrichment limit, meaning it is detecting an excessively lean fuel-air mixture across both cylinder banks.

If the MAF sensor sends a corrupted or incorrect reading, the DME cannot properly calculate the air coming into the engine. You can try cleaning it with CRC Mass Air Flow Sensor Cleaner. If the problem persists, the MAF will need to be replaced with an exact Bosch equivalent.

Any unmetered air slipping into the system after the MAF sensor will cause the computer to register a lean condition. Check the rubber intake boots, the resonance tube flapper, and the oil filler tube/cap for cracks or loose clamps. A mechanic can perform a smoke test to locate these leaks precisely.

A torn diaphragm in the AOS can introduce excess unmetered air into the intake manifold. Fuel Delivery System: If the engine is starved for fuel, it will read lean. Check for a failing fuel pump, low fuel pressure at the rail, or a severely clogged fuel filter.