My stock spider setup had 66 psi key on and 62 psi at idle. The MFI upgrade was 58psi key on and 54 at idle.
For those of you tuning your own trucks, it will run with the spider upgrade decently but it will never be quite right with the factory injector data for the poppets. The upgrade spider uses different injector data programmed into the PCM on trucks that came from GM with them installed from the factory. I snagged the data out of a newer 4.3L truck. The newer 4.3L engines are returnless at 58 psi. When I tuned my van with the 0411 initially I used that newer returnless 4.3L injector data from the 0 kpa vacuum row and copied it into my tune. That fixed the noticeable fueling difference from the spider change on my then GM Goodwrench but otherwise OEM 350 in the van. After the injector data was inputed it ran smoother, better mileage and more power. Ran even better when I corrected the commanded air/fuel ratio for the 10% ethanol in the fuel.
PS I have that data in an Excel spreadsheet if anyone needs it. Flow rate, minimum pulse width, voltage vs kpa offsets and minimum pulse adder are all different.