Audi A4: Performance Loss - Estimated 40 HP

"For a few days now, my A4 Cabrio has been sporadically showing a drop in performance, feeling like a loss of about 40 horsepower. On the highway, I can barely manage 120 km/h in 6th gear, and it's really struggling on even slight inclines. The light for the exhaust system (a stylized engine block) is yellow, but it's sometimes off. Since I filled up with Dutch gasoline over the weekend, and then switched back to "German" gasoline yesterday, the symptoms have been significantly less severe, but they are still present. The workshop, which can only give me an appointment in 8 days, read the error codes."

01282 035 Switching valve for throttle control flap - N239.
sporadically
01259 031 Fuel pump relay J-17 - Open circuit/Short to ground.
sporadically
01375 031 Valves for engine mounting, Level 1 - Short circuit to ground/open circuit.
sporadically
......
Valves for engine mounting, Level 1 - Short circuit to ground/ground fault.
sporadically
17809 P1401 035 Exhaust gas recirculation valves - Short circuit to ground.
sporadically
01262 031 magnetic valve, boost pressure control - N75: Open circuit/Short circuit to ground.
sporadically

Does anyone have a clever idea?

Thank you!

Hello, your symptoms sound like a limp mode situation. In my opinion, this is likely related to the turbocharger or its control system (e.g., a stuck variable geometry turbocharger or a faulty boost pressure control valve). The best course of action would be to have the error codes cleared (if they haven't been already) and then drive the car again, or try to reproduce the limp mode.
Next, read the error codes again (either yourself or have someone else do it) and post them here. Alternatively, check if the VTG (Vehicle Traction Grip) system is functioning correctly. Instructions on how to do this should be available in the technical articles.

Regards,

Sven.

Someone can say what they want, but it also looks very much like damage caused by martens.

If the turbocharger pressure can no longer be regulated, then the system will enter a failsafe mode.
Hopefully, the engine control unit won't be damaged by all these short circuits.
Otherwise, it could get expensive.