Not sure but my box is under my dash and I run the Fitech wires opposite side of the car than other wires but I have heard that the temp sensor can cause issues with tach signal. My battery is in the trunk with ground run up to and bolts to engine.

i did the same I seperated everything trying to keep signals from crossing
still It ran great one day at the racetrack wiredup the nitrous and had to go back to a carb which highly dissapoints me car ran a .30 faster on e 85 and fitech

There is a tach wire and a place on the box it self I have mine fitech tach wire hook to the box. Some of these things don't make sense how some have issues while some don't.