I put the capacitance plates in my -9 and use the Dynon sending units.
In 250 flight hours I am stunned at how accurate they have been. Enough so that I have never bothered tuning the fuel flow. If my Dynon EMS tells me I have four gallons left (almost an hour?s worth of fuel with the old engine), I have exactly four gallons left.
If you elect to go with these, when you put the BNC connector in the tank, cover it completely with proseal, I mean, make it look like a mountain in there. The BNC connectors can leak out the centers, so use a LOT of proseal. Got it? Use a bunch of proseal on the BNC connectors!