You guys might be over thinking this. In theory that calculation is possible if.
You have perfect carburation (but you don't) you have perfect timing (but you don't) Your manifolds are 100% efficient (but they aren't) your fuel burn is based on top output at stp (but it isn't, its an average) and so on. If we think about it, we can add at least 50 more things that will affect your fuel/hp ratio. but if your setup was perfect than 2gph for 100hp is closer.
