Standard Continental sensors are supposed to send 50Hz with Gasoline and 150Hz at E100.

I acquired a couple of eBay Conti sensors that sent 80Hz and 82Hz in pure Gasoline (72Hz and 74Hz in free air respectively). I wonder if some of these generic sensors have gotten sold into the supply chain or if the default specs have changed. Where did you buy yours from? The generic seller told me that their sensors all behaved the same frequency response-wise

I've currently got a (think it is genuine) Conti sensor that sends 50Hz in free air and 55Hz in gasoline.

If you want to calibrate your sensor to cope with a skew reading, have a look at my flex-fuel thread. I can send you arduino code and circuit for sensor calibration.

So how does that work? Does arduino need to sit inline with the system or is it more like a flash?

So does the arduino reprogram the internal cpu on the FF sensor or does it retranslate the signal to the eca unit

Arduino sits inline with the ECA and reads the frequency sent by the ECA then sends out whatever output you program into it based on the frequency read. It does not reprogram the ECA sensor.

Hmm. Might be an option, trying not to complicate the circuit too much. Plus I don't have an arduino

SUCCESS!!
Turns out it was the FF Sensors. I bought one from GMPARTSDIRECT.COM and it worked. Turns out there are knockoffs out there. I'll post a picture forthwith in order to highlight the differences. Really can't tell until you get the two units together.

Awesome! Glad to hear that it all worked out. Did you not get an FF sensor with the Zeitronix kit?

Nope, they're $180 with zeitronix, i got it for $65 at gmpartsdirect.

If you take a look at the picture here. The top one is a chinese knockoff FF sensor. WOuld never have known if I didn't get a good one.
Note it says Made in Mexico but I doubt it.

If you look at both under the light, the GM one is obviously molded while on the knockoff you can see very lightly there are machining marks all over it.

I guess what I meant to ask is if you didn't initially get one with your kit.