The Deakins articles are quite good. But the oracle is the engine operators manual. Hardly anyone uses them anymore, but the two I bought for engines I fly are excellent. At the end of the day, the guys that wrote them (on manual typewriters) almost certainly have more engine dyne time than anyone else. The 2 engines for which I have manuals have a lot less discrepancy between the Deakins / GAMI leaning procedure than Deakins would have you believe.