I have been using Sprinter (my first Suzuki machine) for over an year now. I have been with this mechanic for the last one year now and never had issues with this mechanic. I am fully satisfied. He is good to know what rider actually wants. He use to tune my bike according to my riding style. Tuning intervals increase marginally, bike has become big time fuel efficient very very light in ride. In short he knows everything about a Suzuki technology in bikes.
Many a time I asked stupid questions, asked some modifications, every-time he replied sensibly and I got a satisfied answer.
Just to mention, initially I also tried 3 - 4 other mechanics (who I personally know as good) but they were not as good as this guy. Except one senior mechanic @ Mehran motors, Suzuki show room at Akber road / Burns road. He (Abdul Razzaq bhai) was also very professional. Only problem is time for me. I live in North so it is almost impossible for me to go there and that to in Saddar (a big pain) on regular basis.
The mechanic at Nagan chowk is equally good as him.
You might want to give him a try, a tuning from him. See if could find any improvement.