As far as I remember, my Gli 2011 March Crystal lights version had no catalytic converter. Plus your car is driven around 50k catalytic converter should not be clogged as such but it is worth getting it looked at.
I should suggest using a good quality petrol cleaning additive (any good imported brand from a reliable place is fine), and put in high octane a few times. Try to see if the sound improves and performance goes up.
Here is a list of what you should do in order
1) Add cleaner and high octane and see if it helps
2) if it does not, have spark plugs replaced complete tuning done and reset the computer
If the above do not work (they should inshAllah, its a new car)
3) Have its air to fuel ratio checked
3) Have fuel injectors cleaned and the fuel pump checked
3) Get a compression test done (Especially if the car has been driven on CNG)
My brand new gli '16 gives me knocking and poor acceleration on bad fuel!