Hello all, just got done doing this and figured id make a write-up post about it.
I wanted to add boost by gear to my 2002 with a Speedyefi PNP. To use boost by gear obviously you need the ecu to know what gear you're in. The easiest way is using the stock vehicle speed sensor to then calculate the gear based on rpm and speed.
The speedyefi did not come with the stock vss wired in as a useable input, so you have to wire it in yourself.
The speed sensor doesnt have a direct connection to the ecu, it is a VR sensor that ac signal from the sensor itself to the gauge cluster, where the gauge cluster converts this and sends feeds the vss input to the ecu.
The cluster provides a ground signal or floating , and the pull-up makes it 5v, and gets shorted to ground when it's active.
To use the stock vss, you need to wire the stock vss pin to an unused digital input, and then wire a pull-up resistor from 5v to that same pin.
This is as simple as it sounds, tragically, I did not take photos of my board when i was done after I had wired this in. But I did take a photo before and drew on it in paint for a visual reference.


red is the vss wired to the digital input orange is the resistor wired from 5v to the same digital input

I did this on the backside after removing my ardunio mega 2560 board. it all fit nicely in there when I put it back on. I suppose you could solder to the long 90 degree pins, but that would be hard. just do this on the bottom.
When this is done, put it back together, and enable vss and gear detection. Set it to the digital input pin you used, in this case, my options by the boost and flex were D20, and D21, so I set it as pin 21.
I set my vss up in pulses/kmh, when I tried pulses/mile, the speed was off. You want to drive 60/kmh, and hit the button to calibrate it. Boom, vss working.

 

That's really odd, I could have sworn that the VSS on NBs is a VR sensor, ie it generates an AC voltage signal. In fact, I'm pretty sure I measured this on the bench when I was screwing with mine. I wonder what your 5v pull-up is doing...

 

It is, it sends that ac voltage to the cluster which converts it, then the ecu gets the input for the vss from the cluster if im not understanding it wrong.

 

Ahhhhh, yes. I don’t have a cluster, so I am reading directly from the sensor. This might warrant clarification in your post, which is very helpful btw.

 

Fixed!