Boxer Manifold Pressure Sensor Issue

Sounds familiar. I had similar issues with my Boxer. Is it idling rough, too? Check for vacuum leaks around the intake manifold, that was my problem. A bad leak can throw off the pressure sensor readings.

Interesting. I haven't noticed rough idling specifically, but the other symptoms are spot on. Where exactly should I be looking for these vacuum leaks? Any specific areas known to be problematic?

It's tough to pinpoint without looking, but check all the hoses connected to the intake manifold. Also, where the manifold connects to the engine block. Honestly, with those symptoms and my past experience, I'd suggest getting it smoke-tested at a workshop to find the leak quickly. They can also confirm the sensor is bad.

Thanks for the advice. I took it to a local mechanic, and you were spot on. Large vacuum leakage was the issue, which damaged the manifold pressure sensor. Repair cost me 235€. Runs like new now!