Avensis Diesel Reduced Engine Power

Whoa, that sounds rough! A lean condition could definitely cause those symptoms. Have you checked the basics like the mass air flow (MAF) sensor or maybe even the throttle body? A dirty MAF can mess with the air/fuel mixture, and a sticky throttle body can cause some weirdness too. Though, I'd expect to see issues at idle if the throttle body was the culprit. Could even be the EGR valve sticking open. When was the last time you had a good look at the air filter? It's probably injectors though, just thinking out loud. But you are not actually sure about the injectors right?

I haven't checked the MAF or EGR valve specifically. Where are they located on this engine? I am not sure, no.

Okay, so you're not sure about the injectors and haven't checked the MAF or EGR. Alrighty then! Seriously though, without proper diagnostics, we're just guessing here. While a dirty MAF or EGR could contribute, your symptoms do point towards a potential fuel delivery issue. I really think you should have it checked out by a mechanic, or someone that can run proper diagnostic procedures before something gets damaged. It's a pain, I know, but better safe than sorry!

Thanks for the advice. Took it to the shop, and it was indeed a defective injector. Repair cost 515€