you rely on engine braking to help hold your speed. As this thing will instantly start pumping fuel in to get rid of the lean state, which means you no longer have any sustainable engine braking.
Isn't engine braking a function of the air that can move through the motor? So if the throttle plates are closed, airflow is restricted and the motor can't turn as fast.
I was sort of surprised when I put an AFR gauge on mine that the mixture actually went a little richer (sometimes down to 12:1 for a moment) when letting off the gas, but I still slow down. Otherwise I'm at 14-15:1 at idle, high-13/14.5:1 at light throttle/cruise, and mid-12:1 wide open / accelerate or climb hill so think my carb is tuned correctly. Didn't want to hijack the thread but it was interesting and thought it would be the place to share.
Back to CFI - Seems like it would help level out AFR when leaner than the set point, but would only really be noticeable on a cold start or if you run lean for some reason (like an elevation drop). Could be handy for some people - halfway to EFI and with a soft-fail.
Would be super interested to see data logs showing RPM, throttle position, and AFR from the same engine and properly tuned carb with it enabled or not.