8.1 to 6.1

how much of a difference in added fuel pressure is there between a 8.1 disk to a 6.1 i know they are for 24 lb inj to 30 lb inj...just wondering the difference for about 7 lb of boost if the base pressure is multiplied by 8.1 and 6.1 repectively would the 14 lb of fuel pressure between the two be enough to support the fuel need if i went to the 6.1 ?? if base is set to 40 lbs the 8.1 would add 56 lbs to it at 7 lbs of boost?creating a total of 96 lbs? whats the optimum fuel pressure to start with without a dyno around to check? i can check plugs to see about running lean as i did with nitrous , supercharging is a new experience to me...anyway thanx again , Rich