I experimented with an MBC my already modified WRX and the drivability was terrible! The PTFB was way out of hand and my EGT gauge pegged with little effort. You'll easily blow the motor if you don't know what you're doing and you don't have a boost and EGT gauge to monitor things closley.

I would avoid the whole MBC route and spend the money on something like ECUTECK or AccessECU/Port.