Folks forget, the 'HP' Series of Holleys are rated @2"Hg delta, not 1.5"Hg, ....a 1000HP is the equivalant of an 866cfm std. 4150 DP. The venturi & throttle blades are the same dimensionally as an 850DP. No choke, improved airhorn contour, & tunability are the big plus factors. With the annular...