Hey guys for those who are using a DET3 on a RB20, the install manual (for R33 RB25) is the exact same. However, it tells you to use configuration 7.
I followed it to the T, but it asks for "NUM signals for 720", I had it at 4, make sure you set it to 6.
I had launch control set at 5500, but it was kicking on at 3000. I was looking at the car just idling, and I noticed that even though my idle was about 800-1000 on my cluster, it was showing almost 1500 on the software.
Set the number from 4-6, and viola, reads about 200 or so RPM's difference (my car is a bit old, so I'm assuming the tach is just old and tired).