Carb tuning help

hmmmm.. i opened a few old carbs just today.. checked if it was.. i fond all of the metringblocks i had was the same size.. exept for a pretty new 750.. no i had 4 650 mtringblocks 2 750.. and 1 850.. all metringblocks had same pvr holes.. mystical.. i think maybe u gys are refering to some aftermarket or the newer, maybe bigger like dominators have larger?.. mainly the hole in the pvr itself are alot smaller than the 1 in the block.. but its the spring tention that is different and u could tune the amount of vacum needed by changing the pvr