Don,
I have no experience with the FI Tech unit, but your chase for mileage improvement seems to be ignoring the fact that you're pushing a brick through the air. IMO you should be over joyed with the fact that you can get nominal 16MPG with a full fendered Model A. Why not just enjoy the ride, and let the mileage land where it lands. If you took on the project of building a street rod based on a mandatory fuel efficiency then I'd suggest that your base premise was flawed. Enjoy the fact that you have a nice '29 roadster that you can have fun with, and quit worrying with the MPG. Just my $0.02 on the subject, and it may not be what you want to hear.