Boosting RFID sensor range

[vette427-sbc]

I am designing an RFID proximity key ignition system for my car and this is the last "snag"
My current passive tag RFID system only has a range of ~3" I would really like it to be somewhere in the 2-3ft range. Is it possible to take my passive tag system and create or buy an active tag to boost the sensing range? Any EEs out there? I dont really want to spend $200+ on a kit that is made for retro fitting a push start system. All I need this to do is trigger a single relay.