Scott---we've plumbed quite a few of the FT60s in all kinds of experimentals, (probably close to 200 now). That doesnt make us experts, but Steve and I think we have a preety good grapse on the situation. Generally speaking, the FT60 is less prone to attitude that the Flo Scan. More robust, and the design leads itself to simplier plumbing, like angled fittings at the body, etc. That being said, we know of a couple of anomalous readings after install on different model engines, different avionics, and different mounting locations.
In all three, the FT60 had been previously mounted and flown, giving the pilot the baseline readings they assumed were correct. I say 'assumed' because there wasnt anything else to go by. So when changes to the fuel systems necessitated a location change for the transducer, a competely different set of numbers occured, that wasnt necessarily corrected by a change in K factor.
On 1 of those, the client went through a pretty precise test program, by moving the transducer to different locations (yes with different plumbing) and recorded the findings. Anything downstream from the servo read differently than upstream, and (as I recall) the differnent upstream locations read different from each other. Changing the transducer repeated the readings, with no apparent differences in units. Quite puzzleing. That one is still being tested---I think.
The other one I'm familiar with , after MONTHS of headaches, and several unmentionable words, the client changed to a 3rd different unit ( if memory serves me correctly) and boom, the readings where much closer inline to what you would expect, without the anomalous drop off in reading flow.
As far as I know, these are the couple where there wasnt a logical explanation for the readings. In your case in building a 14, Vans dictated in the FWF section to locate the transducer under cylinder 4. WE've heard of a couple where there were apparent failures of the units do to broken wires at the body, but otherwise no other reasons. I guess anything electronic can fail at anytime--like everything else, but overall with the thousands of these units flying, they've proven to be reliable, even it aerobatic flight.
Tom