Actually, I've read more than a couple reports from owners who had shops also struggling with this type of code, and throwing lots of parts because they don't diagnose properly. The correct approach is to use a scope to evaluate the cam and crank sensor signal wave forms, to find out what irregularities show up. However, very few of us who DIY, owns one of these fairly expensive tools, so that type of diagnosis unfortunately is not happening for most of us.
Was there any change in performance since this code started showing up? How about the oil maintenance - were oil changes always done within the vehicle's specified mileage or time interval?