first check your air filter is not clogged
Contorlling the RPM is neither task of Emulator nor the advancer even on CNG. its the task of ECU or ECM (Engine control module) which controls it based on the signals from IAC (Idle Air control Valve), and MAF (Mass air Flow sensor) and O2 (oxygen sensor ). get chekced with ECM scanner (avialable at 3s dealers and at Jahangir Garage nation wide) if their is any code of these sensors then get it fixed . either sensor could be faulty or its wires may be loose or shorted together etc, .
if neither is problem then your throttle body may be dirty due to excessive carbon on CNG. it can be cleaned with petrol after openeing, or a carbuartor cleanor spray without opening the throttle and jsut by removing air filter assembley for more information you can contact at 03336530527