Hi, i just bought an 2005 audi a4 1.8T with 73348 miles, and the CEL keep poping up, everytime i took it to the shop and get it fixed and it pop up again the same day or the next day, what exactly going wrong with it?

Parts already replaced:
Air Mass Meter MAF
OXYGEN SENSOR BEFORE CAT
Boost Control Valve for Turbocharger

I've done all these in a private shop, the machanic did a vacumm leak smoke test and found 2 large leaks and had it fixed, the light was off and i drove it for 1 hour it turned on again, I seriously dont know what to do now, it seems like the light will just pop up no matter how many times i took it to the shop.

Any ideas or suggestions?
thanks in advance

 

did you ever get the 0171 0507 codes resolved?