i dont have a factory alarm. i purchased a code alarm. it is really good. right now i just have the keyless entry and flashing lights options. i plan on upgrading it to remote start and remote power windows instead of remote door silenoids for when i shave my door handles. these are all things you should consider when buying an alarm. mine cost $250 installed. and those options i just mentioned run it into the $430 range i believe. another cool option is remote stereo turn on.