We did the porting for Apten from the beginning till Dec 2004.
We stamp a series of numbers on the blower case under the snout to the left or right and it should have stiegemeier stamped on the oppisitite side( this can be seen while blower is on the car) Every blower is and was stamped with the numbers, that is how we keep records. We do add clearance when needed now and highly recommend stripping the rotors.
Thank you