Ed,
I don't think we're on the same page at all.
<...  the fuel flow will already be relatively high ... heat of vaporization of that much fuel will probably already have the temperature of the air near a low point ...>
Let's suppose for the moment that the default injector is at the BLOCK.  NO fuel gets injected at the top of the runner.  We can further suppose that absent outside influences the runner temp is very close to the ambient temp.

Therefore, if the ambient temp is 25 F (the temp to give you DIE at TO rpm, say 5500) you would keep injecting ALL of the fuel at the block.  Now if the ambient temp is 45 F, you will need to cool it A LITTLE - so you inject 20% of the bandwidth at the TB and 80% at the block.  That 20% vaporizing in the runner brings the charge temp down to 25 F and the magic happens.  If the ambient (default runner) temp is 65 F, you will need to inject 40% of the fuel delivered by that runner at the top and the remaining 60% at the block.  If the ambient temp is 95 F you will be injecting most of the fuel at the TB for maximum vaporization in the runner, giving maximum cooling of the charge to bring the charge temp down to 25 F which corresponds to your DIE Tr.

If you got into an ambient temp of 15 F, you might want to introduce some warm air from the radiator exhaust to bring the charge air UP to 25 F.

You inject the exact amount of fuel at the TB to accomplish the exact amount of cooling you want to do.  All the rest gets injected at the block.  All the fuel is vaporized as it enters the combustion chamber (just as it is now, in the stock system, where it is all injected at the block).  The engine doesn't know or care how far upstream of the intake port the fuel got vaporized.  We are SPLITTING the injection task VARIABLY between the TB and block injectors to achieve the degree of cooling we want.  The total charge doesn't change, only the portion of it that gets injected upstream to cool the intake charge.

Like the fuel control will compute the bandwidth of injectors necessary to deliver the calculated amount of fuel to that particular runner.  Then the calculated bandwidth will be distributed between the upper and lower injectors so as to deliver just enough of the charge to the upper injector to accomplish the cooling we want.

Hope this helps .... Jim S.
 

Ed Anderson wrote:
<...  the fuel flow will already be relatively high.  Latent heat of vaporization of that much fuel will probably already have the temperature of the air near a low point ....  Pumping more fuel in might not necessarily result in lowering temperatures if the air stream is already saturate with fuel vapor.  I don't know enough about how gasoline acts in such a situation, so that is just a guess.