Fortuner intake manifold flap issue

That sounds concerning. Has the engine light come on? A faulty manifold flap could certainly cause those symptoms, especially the reduced power and hissing. Have you checked for any obvious air intake leaks?

Yes, the engine light is on. I haven't spotted any obvious leaks myself. Is there a reliable way to confirm the intake manifold flap switch is the problem before replacing it?

Confirming it without proper diagnostic tools can be tricky. Given the symptoms and the engine light, the intake manifold flap issue seems highly probable. However, misdiagnosis is always a risk. Wouldn't you be better off having a workshop run a proper diagnostic to pinpoint the problem before throwing parts at it?

Thanks for the advice. I appreciate the caution. It turned out to be exactly as we suspected - the intake manifold flap control. The total bill was 465€, including the part and labor.