I had an interesting experience a few months back when i had to get my margalla tuned up. I didn't want to go to the car's own mechanic because he started charging more. So i asked one of my friends to recommend a good mechanic. He told me that he knows a mechanic but he would spend 4-5 hours in tuning the car. I was surprised as tuning does not take more than 20-30 minutes. But I went with him anyway. When we met the mechanic he also told me that I would have to spare 4-5 hours. Anyway i consented. The mechanic opened up the half of the engine, plugs, carburator, head, tappits, crank shaft and washed every part with petrol. Then he fitted everything back and made the settings according to the manufacturer's specs. It took him about 3.5 hrs but when I drove the car, it was like new. A 1995 margalla went to 140kms/hr on cng with full a/c on motorway. I reduced the speed because the car was getting unstable.
Then my father's corolla 2000 model 1.6gli had this problem that on steep roads it could not climb on cng. It was pathetic that a 1600 cc car could not travel on road to pir sohawa. I took the car to the same mechanic and again had to spare 4-5 hours but the car responded excellently after the tuning.
I strongly recommend this mechanic to all car owners in islamabad. His name is Rizwan and his workshop is in G-10 behind the new high court building.