Daeng,

I don't think you would gain any power at all without other modifications that caused your motor to need more fuel. The 02 sensor will maintain the mixture and remove any extra fuel except at full throttle, unless you add so much fuel that it is beyond the ability of the 02 sensor, in which case your motor will run very poorly. Even in stock form, the fuel injection probably has sufficient flow for around 160 hp. Your problem now is airflow in and out of the motor. A fancy air filter will not help (though cleaning out the airbox and opening it up will not hurt). You really need a cam that lets the engine take in more air an exhaust that helps get more air out. Even with these mods, you will not exceed your fuel injection's limits. IPD and MVP sell these parts, as do some European tuners. You can do much more, like installing a performance head and a fancy engine management system (at perhaps $2000 each, versus perhaps $1000 for just the cam and exhaust. You can also attempt to turbocharge the motor you have, keeping the boost low and using salvaged 740/940 Turbo parts and some custom work.

Philip Bradley