I know this is an old thread but I can't help but comment on this.
There seem to be two types of mechanics I am seeing here.
1 - Parts changer - Take everything said on any forum as the gospel and start changing parts, hoping that one will fix the issue. This is wasteful the and expensive route. Sure you may get lucky, but most likely you will spend needless time and money. I.E. (It's your valves = engine tear down).
2 - Diagnostitian - This person listens to the forum members that make sense and explain what and why they think the issue is. Now they can be incorrect as they don't have the car in front of them, but this is a good place to begin your own diagnosis.
Did you get that, begin your own diagnosis. Spend some time studying the theory of modern vehicles and apply your knowledge. Just because one person had a problem and they fixed it with a part has nothing to do with your vehicle. Use a systematic approach and rule out the systems and parts that others just change based on a generic code. Lend more credence to those that obviously have experience (I.E. Ford techs) than you do to the 16 year old repeating what his sisters boyfriend told him.
Enough of a rant. It's your car, your time and your money so you choose how to spend it. Me I have been able to fix every problem that I have had on every vehicle I have owned. During that process I have learned a great many things and solved a great many issues at minimal cost.
In the end I just hope a few people heed my advice and avoid being a parts changer. Save your money and expand your mind, it's very satisfying to problem solve and correct any issue and save thousands.
TTFN