Free flow front box

[Volksie 2.0]

Good day i decided just to let my 2.0 9n3 polo sound nice, but not too loud to change the front exhaust box to a more free flow 1 then the original 1 claimed to be free flow what i notice were this car response was excellent in the bottom range i use to roll at 40km an hour in 2 if i put my foot down she use to excelirante quickly now its like the response up to 3000rmp is so slow and then it goes why would that be so i dont wanna touch the software on the car too make it work if thats what is needed what would you guys suggest i must do? Its the 2.0 8v bbx engine is my only solution to put the old box back? I would appreciate some good advice kind regards Anna-Mari