The only problem is when they are not compared at the same depression with the same method & conditions. If You can get 850 thru' a 250 I wanna see it.....and hear it...
Thats the real question is depression you want to run at full throttle not how much cfm.
I don't know what a restrictor plate flows but it's lot less then what a nascar engine needs, the air still gets minus the pumping loss hp cause of the restriction. My cousins late model pulls to 6500 plus through a two barrel.