I have installed everything from cold air intakes, exhaust and software mods to complete supercharging systems . depends on how much power you want and money you want to spend.
Since Lexus engine design is fairly optimal from the factory, increases in HP from things as K&N air filters or cold air intake may not be worthwhile. If you really want to keep the car and money...
perhaps installing a K&N air filter. there may be high performance computer "chips" available. you would take out an existing chip from the cars ECM and replace it with a high-performance one. be...