I got most of DV books, my 1st and main one I got when was fairly young was Performance and economy which I've probably read a 100+ times, I'm sure that book has influenced how I see performance drivetrain should function. But I've seen very little of dyno/other evidence to back up from him and others to prove his points so I have to take with a grain of salt. But what's good about his books/teaching he practically the only one given the less informed a complete in depth system on the engine/drivetrain for people to use as a basis of understanding. Even if he's not a 100% accurate you could do a lot worse not going with his advice.