This is a Simota cold air intake kit, someone actually bought a proper bottom breather (albeit cheap) kit for this car like it's supposed to. Most people just stuff in an air filter cone in the engine bay that sucks in hot air instead of cold.
Without tuning, this air intake kit is pretty useless. Revert back to the stock air box, go to a parts shop and ask for reborn ka original air box complete assembly with filter.
For cat, you can get a new unit from Honda, or buy used from a reputed silencer shop. Also check spark plugs and buy new plugs for it if required. OEM plugs are NGK IZFR6K-11.
This car, when driven with a light foot should give you 9-10 kmpl easy.
Good luck, don't hesitate to ask questions here!