For CNG adjustment go to stadium road RWP. There is a huge shop by the name of CNG complex. These guys are good at diagnosing and solving the problem.
For other mechanical work its purely your choice. If you go to Honda authorized workshops then they will take slightly more but their results are pretty awesome.
Or you can go to good mecahnics in G-10/ F-10. The guys at these places are very used to working on various models of Honda.