It's pretty complex in terms of thermodynamics, gas laws and other physics not readily available to the public. I think the OEMs model these phenomena by experimentation and we'd pretty much have to do the same. Fuel puddling and evaporating off port walls isn't something you can readily tune unless you have all the initial conditions and geometry that GM started with.
However, if you find that fuel is lagging behind throttle, such that you're getting instantaneous lean conditions all the time, you could change the transient tables to trick the computer into thinking there's less fuel than there really is in the port. This would effectively tell the ECM to add more.