I have a 1207747 that I have put on 1965 El Camino, i pick up parts from wrecking yard and some i have bought. For the Vss signal used a Hall Effect chip on the drive shaft, this causes my speed in the data log to be off by about 30% high. In the bin files Mph is used in several places, Everything seems to work, other than some fine tuning, which i am in the process. Is there any way to correct this. Any help or thoughts would be helpful.