I wonder how many vehicles have aftermarket turbo's that need certification

From NSW VSI6

Examples requiring certification:

• Fitting a turbocharger/supercharger to any vehicle of a make and model not offered with a turbocharger/supercharger by the manufacturer.

• Modifications to a vehicle with a power output of 100 kilowatts, which results in a power output of greater than 120 kilowatts.