Vizard is a good writer. However I learned the hard way to be very very careful in assessing whether specific modifications can be applied from his tests or experience to whatever it is I'm working on. All too often generalizations fail when based on too small of a data pool. He is also limited to the format of the SA publications so stuff gets left out.
Differences in exhaust arrangements, stroke/rod, valve timing, etc can effect the intake and fuel distribution.
