Veloster Check Engine Light Sluggish Performance

The symptoms you describe, specifically the check engine light accompanied by reduced power and increased fuel consumption, suggest a potential issue with the boost pressure control system. The pressure sensor, boost solenoid, and vacuum lines are elements of this system. It is crucial to verify that all vacuum lines are securely connected and free from any visible damage. Did you perhaps examine the vacuum switching valve? Pressure drop can originate from a defect there.

Vacuum switching valve, huh? I haven't checked that specifically. Where is that located, and what should I be looking for exactly?

The vacuum switching valve is typically situated near the turbocharger or within the vicinity of the intake manifold. Inspect the valve for any physical damage, cracks, or loose connections. It would be prudent to consult a qualified mechanic to perform a thorough diagnosis utilizing specialized diagnostic equipment. It is my suspicion, considering all the information, that you may require expert intervention.

Thanks for the help. Turns out it was a faulty vacuum switching valve, just like you suspected. The workshop replaced it, and the total cost was around 140€. The car is running great again!