I recently bought a 2007 Audi B7,when driving on the highway for about 20 minutes,my glow plug light started flashing,check engine appeared. My car went into limp mode,I was absolutely turtling,even losing speed sometimes. When I would turn the engine on and off,it would be fine for about 5 minutes,then the same issue would reappear. I didin’t start the car for about 2 days,now I tried driving it. I drove for about 15 minutes,the issue was gone. But the turbo only starts spooling at ~2.8k rpm. I fear the issue would reappear if i drove any longer. Any idea what the issue might be? I’m not in my home country right now,and I would like to know if it would be safe for the engine for a trip home?