[V8] Rons FP Reg hose

[Professor GT gmail]

Ron, 

The vac hose should go from manifold vac to the FP Reg.  It serves to maintain proper fuel pressure. In a bit more detail, what it really does is maintain the correct pressure drop across the injector. You see at WOT there is 0 vacuum, so higher fuel pressure is needed behind the injector to maintain the proper pressure drop so adequate atomization occurs. When man vac increases as at CT, fuel pressure is reduced through the vac signal to the FP Reg, so once again the proper pressure drop, hence spray pattern is obtained. This of course is aimed at efficiency, max economy and engine/catalytic converter life.

Having the line unhooked gives max fuel pressure across the board and results in a wasteful over-rich condition at high vacuum (no-load/idle) conditions which can also shorten cat-con life due to excessive heat from the over rich condition.
 Unlike some may think this does NOT improve max power one bit, because there is 0 vac signal to the FP Reg at WOT anyway. 
Hooking up the vac line should improve Driveability, unless of course the line was disconnected to cover up some other fuel system shortcoming such as poor injector flow.

Hope this helps !

Thanks,

ProfessorGT
(Sent from my iPhone4)