Tach Readings Mystery

After much tinkering and reading many posts here and otherwise, I am STUCK ... My tach doesn't read accurate, to be honest I am not even sure what it reads, so here is my story and I'd appreciate any advice I can get.

I run a stock 912 ULS and my trigger coil tach is connected to a Falken EMS/EFIS, one wire to the EMS RPM input, the other to GND, per Falken tech support. Having said that this is the first Falken Rotax install for them so there maybe a software issue but we do get some readings.

So here is what I tried so far ...
- Installed a 60k ohm resistor in series per some posts I saw, no change
- Used a prop tach to measure prop rpm and then convert with gear ratio of 2.43 to motor RPM, for safety to not overturn the engine
- For trouble shooting purposes, I purchased a standard Aviasport Rotax 912 tach ... no reading at all. It's connected per drawing, + to battery, - to GND and bottom #3 post to same rpm wire going into EMS, tried both before and after resistor, no difference, do reading at all
- Checked and adjusted the trigger coil gap per manual
- Tried both 1 and 2 pulse per revolution setting, and despite manual only 2 gets reasonable low RPM readings ...weird 

I am lost ...
- Why do we get erratic readings in high RPM range, even with 60k ohm resistor?
- Why does the EFIS show ok readings with 2 pulse per revolution count in low range when Rotax documentation says it should be set to 1?
- Why is the Aviasport tach not working?
- I took off and reattached the trigger coils to remove engine from ring mount when delivered ... could I have screwed up the washers to align them to wheel magnets? If that would be the case, how would the engine even run smoothly as it does?

As you can see, I tried a lot and the last nail in the coffin was when the Aviasport stock tach didn't give me any readings at all. I didn't connect both wires to it directly but one wire is connected to the main ground bus and then from the ground bus to the tach but I don't understand why that could be an issue.

Please help and comment AFTER reading all the steps I did take, this isn't my first rodeo and I have found Rotax to be super reliable but this for sure stumped and frustrates me :-( ... HELP!!!

Thanks Robert