Shop manual
Ditto on what jkalchik said. In my early days I was a VW & Porshe mechanic. When you have been factory trained and perty well know the cars inside and out, and then look at these after market manuals like Haynes, I just shake my head in disbelief at the misinformation that they put out and the important things that they leave out.
I only buy factory manuals, or factory authorized manuals for my rigs, it is money well spent.