Algorithm vs. fuel map

[Santi Udomkesmalee]

please excuse me if I have made a huge mistake in understanding these 
systems.  any corrections and explanations would be greatly appretiated.

So my question is regarding the calculation of proper pulsewidths by the 
ECM.  It is my understanding that a system like the Megasquirt uses 
algorithms which calculate on the fly the proper pulse width from the needed 
inputs.  What sort of advantage does this have over useing a system which 
looks up the pulsewidth in a preprogramed fuel map.  It seems that in a 
sequential injection situation at high rpms, the processing power to 
continuously calculate the proper injection would get costly when designing 
a system.  What are the draw backs of using a system with a pre-programed 3D 
fuel map.  I may be misunderstanding how these systems work though.  It 
seems to me that while a preprogramed map might take slightly longer to 
program, it would result in a cheaper and possibly more reliable system.

My second question has nothing to do with EFI, so sorry for asking it, but I 
was wondering why in a V-shaped engine, many performance automobiles 
(ferrari, lamborghini, etc.) used two plenums instead of one.  I understand 
the notion that the larger volume needed when running only one plenum would 
result in slower throttle response, but is that it?  Also, when running a 
forced induction type setup, would a dual plenum design still be a worthwile 
design?

thanks in advance for any light you guys can shed on the subjects

-santi u

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