If you are wantin to do autocross, then i would just get that motor you have in there running good, and spend the money on suspension and good wheels, tires, and brakes. There are guys out there in crxs with d series, runnin faster than just about all the cars out there. Runnin the moton suspension with some sticky ass slicks, and some good brakes. Like one of the instructors told me, its all about the lateral grip. Power aint shit in autocross