LFA Hissing Sound

Sounds familiar! I had a similar issue with my old BMW M3, different beast I know, but the symptoms were almost identical. Higher fuel consumption, that annoying check engine light, and a hissing sound under acceleration. Turned out to be a cracked intake hose. Have you tried checking around the intake manifold and throttle body for any obvious cracks or loose connections? Leak detection spray might help pinpoint the exact location.

Thanks for the tip! I'll definitely check the intake manifold and throttle body more closely. Where exactly did you spray the leak detection spray? And did the check engine light give you any specific engine misfire codes?

I sprayed the leak detection spray around all the intake hoses and connections, especially where they clamp together. The BMW gave me a lean mixture code and some misfire codes on a couple of cylinders, which made me suspect an air leak. Honestly, with those symptoms and the mileage on your LFA, I'd bet it's an intake hose. Could be a pain to reach, though. If you're not comfortable tackling it yourself, a workshop will sort it out quickly.

Thanks so much for your help! I took your advice and found a split in the intake hose. Replaced it, cost me around 100€, and all the symptoms are gone. Fuel consumption is back to normal, the check engine light is off, and no more hissing sound. Really appreciate your insight!