Short history first: A few weeks ago I installed my Holley AFPR and set the pressure to 46 psi w/o vacuum. I've been really bust with work so I didn't pay much attention at first to how it ran.
I thought it was running better but I've noticed the last couple of weeks that my mileage on the freeway has been significantly lower - 23-21, easily dipping into the upper teens at times - where usually it's hovering around 27, sometimes 24-23. I've also noticed that it's not running well (as in rough, not as responsive) but then takes off hard kind of like a switch is flipped when you hit it to half throttle or more.
I thought that perhaps I have a leaky injector, maybe chewed up a plug, or something like that. Tonight driving home I was thinking aobut it and tried bumping up the fuel pressure by about 10 pounds. All the symptoms immediately went away. It's now back to motorcycle-like throttle response, mileage went right back to 27 at cruise on flat sections of freeway, no more rough idle, no problems.
I have the Bosch III injectors which are supposed to be 24 lb/hr at 43.5 psi and a PCM4less tune. So I'm wondering if the tune is just that far off, are the injectors undersized for the new engine, or is running almost 60 pounds of fuel pressure "normal" for my setup?
Sorry, but I don't have any data logging available.
previous Vettes: 84 CFI auto, 99 Nassau Blue 6-speed
current Vette is a Turquoise Metallic 91 automatic, 3.07's, Fast Burn heads, SD LT-4 cam, Bosch III's, Accel Super Ram & 58MM TB, LT-1 manifolds, Magnflow catted Y, Flowmaster direct replacement mufflers, 1984 Z51 springs, Koni's, C5 brakes, 275's/315's, VB&P 32mm front sway bar