Flow numbers and max HP potential

well there's gotta be more than 10hp difference for 4mph faster at that level I would've thought...perhaps the rule has its moments as well and 165 is normally an 8.14.....was it a stick car?...we got a CE car here with a Lenco, runs 7.39@185 which is 4>5mph up@2550lb. Anyhow the slide always was different slighty to wallace.