I dont have an exact answer, but there is such a thing as too much, we believe the last time i was at the track, my lack of being able to build even 5 psi at times was to fuel....i was not able to get enough runs in to realize it and fix the prob, i do know that lowering the pressure 1 psi enabled me to go from 4 lbs to 7 on the line (this is even flooring the pedal) which i had never had to do until i used the chip i tried that day.
I wish i could go and check it again to see what types of 02's i was seeing, but i would guess in the 840s or more...
Dan