help! iswara engine choking

[icyd]

my car engine experiencing choking or 'semput' at low rpm from 1-2k.it used to have good torque around this range but now i have to rev till over 3k before shifiting only can feel the power.fc is high.i believe this is tuning problem.but the mechanic i referred to said tuning ok already after listening to the engine sound.any good workshop that proven to do good tuning?anywhere around klang valley.please recommend