This car has no engine tuning parts. Sorry the air filter is not a tuning part. Not when your intake duration is fixed. You can't buy cams for it either since you want to rev kaw kaw. Buying noisy exhaust also will not make your ca go faster. Since your engine dumps a fixed amount of exhaust gas from the fixed engine capacity.

You want play engine tuning, go for turbo cars. N/A engine after RM20K also cannot get 50HP like turbo.

Turbo car ECU reflash 20-30HP. By the time you dump in filters and exhaust it would be 50-100hp more already. Stock NA 1.3cc 1.5cc how many HP to begin with? Even Honda Type R N/A engines top out at 200HP stock. And when you want to milk out another 20HP on that Honda, you already know half the cost of the car already gone to look for that 20HP.

NA tuning HP increments are too small. Turbo gains are bigger. Dun forget by the time you touch the cams, the car is not everyday friendly already.