This won't work on the 2008 Sport & GT's (don't know about the 2007's) without an original 'chipped' key... 'cause they also have an oem engine immobilizer system installed... can't drive the car away by hot-wiring or pulling the keylock...
http://www.mazdausa.com/MusaWeb/pdf/specs_features/veh_specs_MS3.pdf
2008 Mazda MAZDASPEED3 Handling, Ride & Braking Standard Features
- Four-wheel ABS
- Brake assist system
- Four disc brakes including two ventilated discs
- Electronic brake distribution
- Electronic traction control
- Immobilizer
- Front limited slip differential
- Spacesaver steel rim internal spare wheel
- Stability control
- Strut front suspension independent with stabilizer bar and coil springs, multi-link rear suspension independent with stabilizer bar and coil s