At 12:45 PM 10/2/2003 -0500, you wrote:

I understand that the vacuum port
causes a change in fuel pressure as the manifold pressure changes, but I
don't understand why we want the pressure to change.  This seems like it
would make it more difficult to tune the EC-2.  What am I missing here?
As I understand it...
 
I'm guessing that it makes it a little easier to program, because it takes away a variable.  Think about it this way, when you open the injector, fuel sprays out.  It sprays at a rate that's not just related to the fuel pressure, but to the difference between the fuel pressure, and the intake pressure. 

Well, that makes sense...

In an extreme case, if you had 10 psi of boost with a turbo, and only had 10 psi of fuel pressure, opening the injector wouldn't spray any fuel at all. 
 
 The pressure referenced regulators keep the fuel pressure differential the same across the board, so your injector flow remains constant.

I can see where that would be good, as long as the EC-2 fuel map knows how to adjust for the variations in fuel pressure.  So, then the EC-2 will automatically adjust for my "poor man's turbo (ram air system)?

 
 
 For lack of any better setting, I adjusted mine for standard 43.5 psi.
 

Sounds reasonable.  I initially set mine for 45psi, but there's an adjustment screw and know how to use it!  However, my guage is really an oil pressure guage and probably isn't sensitive enough for the accuracy needed here.  I'll wait for my EIS to set it more precisely. 

Thanks for the lesson in fuel pressure regulators,
Mark S.