Big overlap cams and EFI

[Joe Boucher]

The guy at Turbo City that will burn custom prom chips for GM EFI told
me the maximum intake duration he can burn a chip for is 220 degrees.  

What is the problem?  It 's centered around the vacuum signal, correct? 
Is the MAP sensor incapable of keeping up with the rate of change or
magnitude of the signal?  Does the vacuum get too low (air pressure too
high) versus the map in the prom?  If you didn't care about emisions,
could you program the prom so the manifold pressure is ignored when the
throttle position is at idle and just squirts a certain amount of fuel
based on coolant temperature?  With a MAP based fuel management system
is the fluctuation of the vacuum signal at low RPM's too wild versus the
sampling rate of the computer to determine the dwell of the injectors.

In other words, I don't have a clue why this is.

Thanks, 

Joe Boucher
'70 RS/SS Camaro '81 TBI Camaro
Bedford, TX