2015 1.6 TDI Skoda Octavia elegance loss of power at high speeds. Before I describe the fault here is a little bit of context for the vehicle. The vehicle had a timing chain fitted in March it has been serviced each year and runs fine the engine is quiet there are no weird noises and operation of t vehicle is smooth. I got the car in September and was told that it loses power on the motorway. The vehicle was taken back to the mechanic who did the timing belt and was inspected no loose vacuum lines were found or loose fittings. The vehicle was timed correctly. When you accelerate mainly on the motorway above 3000 RPM about 75 miles an hour the vehicle will start to slow down, your foot can be flat on the gas but the vehicle will still lose speed. It will slow all the way down to 45 miles an hour. Gradually the vehicle will speed back up but as soon as you come to a hill the car has no power and slows back down. This whole time your foot can be flat on the gas. The only way to make the car return to normal is to pull over and let the engine cool for 10 to 15 minutes. When you lose power the ribs do not jump up but stay consistent. There are no weird smells it just feels like the car is gutless you can tap the gas quickly to get a bit of speed back but that's about it. In my mind it feels like the turbo is stuck open unable to make any boost. When the fault happens off the motorway the vehicle has absolutely no power to go up hills and has almost stalled there is a small faint squeak that comes from somewhere in the engine when changing gear and using the clutch when the vehicle is in this power loss mode. This fault primarily happens when the engine is warm and under acceleration. I took the vehicle to two mechanics both of which were unable to find any fault codes, and no warning lights have illuminated on the dash. I have had a clutch and a new flywheel fitted to try and fix this fault. There was evidence of the clutch getting hot, but the fault persists although not as severe. I have fitted a new air filter thinking airflow may have been restricted this is not fix the issue. I have driven the car with and without the front assist features, as one mechanic said the brakes could be activating. The vehicle still slows down with or without the front assist. I've just fitted a fuel filter and we'll see if that affects anything? The only other thing that I can think of is that the heating is not as good as it could be inside the car and I read on a different forum that guy had a similar problem with an older Octavia 2002 I think where he replaced the coolant temp sensor and the fuel philtre and that seemed to fix the issue. I think that my showed it is the one with the silica bag in the heating system and it does look like that there is sediment in the expansion tank and over this could block up the heater core which would reduce the heat but would itβ cause heating issues and make the car think its too hot and slow it down. I have driven previous vehicle in limp mode before, and though you do lose power you are still able to drive consistently. I do not think this is limp mode. But I may be wrong. If you have any advice for help I would really appreciate it. Thanks Davis