well you'd get at least 3 things that would help mileage.

1. decel fuel cut, you can turn off fuel 100% on deceleration, i'm not sure if the stock ecu does this?

2. you can run it slightly leaner, although its possible that mbz/bosch already have it fairly lean in certain places

3. sequenital injection: basically if the mixture shows up at the right time, you can get the same mixture to the cylinders as before while using less fuel

also you could have a stronger more modern ignition too, and eliminate the distributor