I don't know anyone that has used Speed Secret books, but I believe there is a particular bright blue car for sale guaranteed to drop your laps times. Some say it can't be caught, the white whale, if you will, but they still try and try and try....
I got mine used at Amazon. (Maybe if I bought them new I'd be a better driver.) They tend to be repetitive but Inner Speed Secrets was my favorite. I have 3 of them if you want to borrow them, let me know.
Does the blue car cost less than a set of used books? If so, I could probably afford it.
Peter, if you bought it, you could park it in your garage and dominate the AX series. Until, of course, Papa Smurf builds a new one. You'd really just be funding next year's thrashing.