I can add to what Bilal recommended. I am sure you know where Azhar Shaheed Market is. Just walk down from Azhar Shaheed Market towards Babu Muhalla after say 10-20 shops you will find Ansar Autos. Ansar used to be the main delaer of Charade Parts once and knows a few good mechanics in pindi.
If you prefer Islamabad, my vote goes to Firdous, he is in Fire Brigade Market. I hope this will help.
With greatest respect to Mr. abcdefgh if someone seeks your help, its much better to try and help than make an issue. By the way 90% of the mechanics still dont know much about how a turbo actually works. Take care and be well