I sense your frustration, and likely building anger.
I was the guy that went and diagnosed our field problems (leaks, noises, other oddities) and when our fault, I often fixed them in our warehouse, sometimes in vehicle or I pulled it. (The plus side of having a mechanic assisting running a machine shop)
Try the cylinder cutout/wire pull, many noises related to piston skirt clearance, pin and rod bearing can be isolated by this method. It only takes about 10-15 minutes maximum to complete.
When you eliminate the ignition the heaviest load on these components is greatly reduced, and usually, if any inadequacy is causing a noise, that noise can be greatly lessened, pointing to the causeusual area..
HTH
