Long story so I'll give you the cliff notes version. 2007, CHN613, AC427, purchased new to pull an end dump. The engine got destroyed with ~107,000 miles on it. I bought a used 427 engine out of an '05, shipped it in and installed it. The turbo was non-functional on the replacement engine so I put the original turbo on. Other than some of the coolant system components and the turbo, all engine parts are from the replacement engine including the unit pumps, wiring harness, sensors, etc. I installed the original EECU on the replacement engine also. All this took place in December, 2010. The dirt hauling business hit rock bottom around here about that time so the truck got used very little afterwards. Fast forward to February 2012. We decided to go in a different direction with the truck so we bought a flatbed and over the road it now goes. It runs good, no EECU codes and seems to do just fine. It started the new adventure with around 120,000 miles (roughly). It now has just over 200,000 on it and recently we had to replace the EGR cooler (go figure). Since we had a perfectly good one on the tore up engine, it only cost me some coolant, a reservoir cap and one busted knuckle. I figured it'd be best if I did a little research on cause and effect of this phenomenon so I check the internet and find some really good info. Needless to say, a lot of it was on this forum. I'm kinda thinking along the lines of computer controlled EGR system, data tables, program logic, EGR delete, etc............ I figure someone has to be doing this, right. So I find the guy who's doing it and give him a call. He's like, "send me your EECU and I can reprogram it in one hour." Well, the truck needs to be down three days for that to happen. Now comes my genius idea. I've got the EECU from the replacement engine. I could send him this one, let him do his thing and I still have the original with the factory programming. I discuss this with the guy and he's all for it except he still needs the original. He would create a duplicate program in the replacement EECU that matched the original, then install the mods. This would insure all parameters are correct. Well, this means the truck is still down for three days. So I hang up with the guy and think about it for a while. Now comes my second genius idea. Take the truck to the Mack dealer and let him program the replacement EECU. Better yet, ask him if the programming in the two are the same. So I get them on the phone and explain all this and what I want to do. I'm informed that they need to install the factory program and calibration off each unit pump and the turbo when they replace an EECU. So now I'm thinking, I installed my original EECU onto an engine with different unit pumps. Should this info have been put into the EECU when the engine was replaced. So now I'm wondering how I should address my dilemma. Here's the dilemma: Original EECU programmed to vehicle and current turbo but not to current unit pumps. Replacement EECU is probably programmed to current unit pumps but not to turbo and vehicle. I haven't tried the replacement EECU in the vehicle to see if it would even run with it. I don't know that I really want to try it. Or if I should try it. So what do y'all think. I guess the obvious question is do I even need to be concerned with this? How different is the calibration between the unit pumps? Is there any gains to be had if I were to spend the money and have at least one of these EECU's programmed to fit everything? Any advice would be greatly appreciated.