Commercial systems

[Bill]

Although I am keenly interested in diy_efi, the schedule of my current
project requires that I purchase a commercial system.  I seems that the big
players are Haltech, DFI, and Electromotive.  Does anybody have any
experience with any of these organizations?  I've spoken with them over the
phone and although all seem to be knowledgable, have imparted more than a
little confusion.  I'm told by a competitor of Haltech, for example, that
Haltech is a "bank-fired" system.....meaning that after the calculations are
complete, all 4 injectors on 1 side of a V-8 are fired simultaneously, then
the sequence repeats for the other side, and so on.   Has anyone ever heard
of such a system?  

I'm also wondering about how the effect of manifold vacuum or pressure
affects the rate of fuel delivery, all other factors being equal.  For
example, if a given pulse width results in 10 #/hr of fuel with a given fuel
rail pressure, does that mean "on the bench"?  What happens when the same
injector is spraying into a 10" or 20" Hg vacuum?  Does that tend to suck
extra fuel.  Or what happens when the boost is run up to 20 psig?  Clearly,
its the pressure differential that is at issue here.  And nobody seems to be
talking about modulating fuel rail pressure in response to manifold
conditions in an attempt to keep the pressure differential constant.  Is
this really an issue, or am I making this more complex than it has to be?

Lastly, does anyone know of a commercial system that is soon to be retired
in favor of a later model?  Or does anyone have a funtional DIY_EFI for sale
at this time?  My parameters are as follows:

      Small block Chevrolet motor (377 cu in) in flat-bottom V-drive boat
       (2) AiResearch TO-4 turbos
       Powerglide
       Crank-driven ignition
       Gasoline fuel with methanol enrichment at higher power levels (>5
psig boost)
       6000 RPM maximum

Thanks for any and all information.

                                                                            
  William Sarkozy
                                                                            
   Kalamazoo, MI