This problem consists of two parts: one where the motor can be improved by yourself, and other one when you can't do anything without. But by your own hands you can do not so little. Perhaps one of the most uncomplicated  activities is the replacement of the simple air filter by a sports air filter or a filter of zero resistance, as it is called. This gives an increase of engine power of 4-7% due to low resistance to air flow. This is the amount of power that the engine is spending for pumping the air through the normal filter for fuel mixture preparation.

Such filters are specific and universal. Specific filter on its geometry is the same as regular and it's easy to install it instead of regular one. No engine modifications is not required.

To install the universal filter you should remove the junction pipes of air cleaner and air cleaner box itself in which there is a regular air filter. Usually that all is attached to the air-mass meter or to the  carburettor by the clamp. Instead of it install another junction pipes to which a sports air filter will be attached. Typically universal filters for the first replacement are supplied with all mounting and fastening elements for a particular car and model of the motor. Later you can replace just a filter if necessary.  It should be noted that the sports filter unlike conventional disposable filters does not require regular replacement. For maintenance they are washed by special fluids and treated with special oil. Resource of such a filter depends on manufacturers ranging from 500 000 to 1.5 million kilometers. We supply air and oil sports filters, as well as installation sets for cars and motorcycles from the two largest world producers "Pipercross" and "K & N".

Here you can find a sports filter for your car and buy it. Source:  http://www.dinol.mk.ua/publish.php?id=12