Peugeot 307 cylinder pressure fluctuation

I had a similar predicament with my 307. The symptoms mirror my experience, although I suspected the turbocharger was the culprit. Does the engine feel like it's misfiring, like a disgruntled dragon trying to breathe?

Indeed, it does feel like a disgruntled dragon! When you say similar, do you mean the pressure fluctuation and engine light as well, or just the performance issues?

Precisely. Cylinder pressure was the heart of the matter, which in turn caused the engine light to come on. I would recommend visiting a trusted workshop. In my case, it turned out to be a consequential error stemming from another, almost insignificant, issue. Perhaps it's best to have it professionally examined.

I took your advice and brought it to the workshop. It turned out the issue was, indeed, a domino effect from something minor, and the repair cost was 0€! I deeply appreciate your time and expertise.