After running it in my car, its performance is very good, but after a while its performance drops noticeably. Can you help with resolving this situation? my car is 2.0t and they say the turbo is ok.

 

what do you mean by "after running it in my car"? How long is "after a while"? Did "they" also do any fault code or engine scans when they pronounced the turbo as being ok?

 

e.g; 0-100 kmh takes 9 seconds until 15 minutes after starting the car and then takes 14 seconds. It was checked with the original volvo device, there is no fault code. When you stop and start the car, the problem is fixed, but after 15 minutes the performance drops.

 

I replaced the turbo pressure control valve and the maf sensor. problem not solved. no air leaks. tcv pipes are connected correctly. there is no fault lamp.

 

Sounds like your intercooler is heat soaked and the ecu is pulling timing(less power). You may need a more efficient intercooler.

 

sounds to me like a relay or solenoid is getting stuck when it heats up. turning of the power allows the relay or solenoid to reset. I'd look at testing the boost control solenoid since it suggests your car stopped making boost.