nothing wrong with using a $75 bipes acu and a afpr:

The Bipes ACU (Auxiliary Control Unit) dynamically retards the timing of your engine to protect it from detonation or knock. The ACU uses three input parameters to control the timing: Airflow, RPM, and Intake Temperature. You can pull a total of 14° of timing. Not only will you help protect against detonation, or you gain low-end power back if you keep your static timing at 10* or advanced. The Bipes is a proven device in NA, turbo and supercharged Miatas

autocrossing is a whole different subject