I have been having very intermittent contribution errors for a long time (years actually) but they have become more frequent in the last month or two. I have a 2004 F250 with 230K and it is fairly stock other than an EGR cooler/valve delete. I have been reading a lot on here and other sites, but haven't found symptoms that are quite similar to mine. The contribution errors started occurring just once in a blue moon and then maybe not for another month or two. The errors are always on the driver's side (2,4,6,8) and when the engine is warm, never when cold. Sometimes I will get a contribution error on more than one cylinder but that is rare. It used to act up shortly before getting home in the afternoons on a 20 mile commute in hot weather. Most of the time, the rough idle will just go away on it's own after a short while. I have an Edge Insight CTS to keep an eye on things. FICM voltage never drops below 47v and normally is 47.5-48v. I just updated the Insight the other day and am now able to monitor a bunch more PIDs. I am trying to get an idea of baselines so I can compare when I get the contribution errors. Are there any particular sensors that I should be monitoring. I have added IPR% and ICP psi. I replaced the fuel injection harness recently even though I have not been able to find any signs of chafing on the original harness. I don't like the idea of throwing money blindly at a problem, but I figured replacing a 15 year-old wiring harness wasn't a bad idea. After replacing my glow plugs and harness last year and seeing how brittle the connectors were, it made sense to me. Since replacing the harness, cylinder 6 contribution errors are far more common and only a couple of times on other cylinders. I am going to order a replacement injector for cylinder 6 since that has become an almost sure thing. Any recommendations for other work while I am swapping out that injector? Should I replace the o-rings on the other injectors while I am in there? I just bought an ELM327 doodad so I can play with forscan, but it sounds like I need to look into an IDS clone for doing more in-depth diagnostics. I installed a fuel pressure test port while I was replacing fuel filters this weekend (which looked fine), but need to get a longer hose for my pressure gauge before I can get any dynamic readings. Sorry for the long ramble and all the questions, but I would love to get my truck back to where I have some confidence in it.

Thanks,

pat