Lets say an engine is running lean on stock injectors even with the FP maxed out. It needs 310cc injectors.

If I put in 450cc injectors and lowered the FP, is there a chance in hell I'll be able to get in the neighborhood of right A/F ratio with a stock ECU?

 

Yes, provided with the proper fuel pump.

What car and what fuel pump you running?

 

For the time being, stock LS fuel pump.

I know for a fact there is enough fuel capable of being delivered for the time being (break in, under 5000rpm). With the MAP sesor unplugged, I am running rich. No matter with what timing and FP with the map sensor attached, I run very lean.

 

What fuel PSI you at? and what FPR you using?

 

I will run lean with the MAP sensor plugged in all the way to 65-70psi.

With the MAP sensor unplugged, I will be fine even at 45-50psi.

I've got a B&M FPR.

 

Ok, leave the map sensor plugged in, and unplug the FPR vacuum hose.

What is the fuel pressure at?