I have a similar conversation with people pertaining to what is highlighted above Scott.
While I'm not the world's best automotive diagnostician, I try to educate people that the code that is set is merely the closest one that matches an existing condition(s) or set of parameters and also that the ECM is ONLY interpreting the data it is receiving, it is up to the mechanic to methodically think through said data and perform a proper diagnosis, nothing more. The codes aren't magic like the numbskulls at the parts stores try to convince people they are as if anyone who reads a code can just replace a part and be a self-proclaimed mechanic.
I also explain that parts stores exist to sell parts, nothing more.
All that being said, I have also discovered, especially over the past couple of decades, that the vast majority of the time when dealing with electrical diagnostics, the problem can be traced back to a connection or wiring issue much more often than a failed part, I would say 80% of the time it is a wiring issue. So, with that knowledge, why is it that the first reaction by most people to start throwing parts at something. I have had more issues over the past few years in particular be traced down to wiring issues and not necessarily a failed part. If I were a gambling man and headed to Las Vegas, would I throw money down on a 20% bet or an 80% bet?
These days I go into a diagnosis with the mindset that I am going to find a wiring or connection issue and I am correct approx. 8 out of 10 times. I also continue to use the 4 C's, Condition, Cause, Correction and the most important one, CONFIRM. If I can't confirm the repair I go back to step one.
I still am not 100% certain that the intake duct IS the culprit here, but I can confirm that it is in fact A problem. However, by looking at all of the new parts on this car, it appears as though a parts bomb was tossed at it with no real diagnosis. I did review the fuel trims and O2 sensor data, but it was skewed because of it being in open loop and with the warmer temps of the shop, it really went into closed loop relatively quick and didn't run as poorly as the owner's description. I think I may park it outside after getting it put back together to confirm, but I also noted it appears to have a leaking water pump and I really don't want coolant all over my shop apron.

At this point I'm not sure how much or how deep he wants me to go into this as he is perfectly capable of replacing a water pump, so I guess that's another conversation, but it's ******* coolant in my shop.