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Wow. I don't pay attention for just a couple of days and we're up to four pages...
If anyone in the world could market a 1000 horsepower 100 mile per gallon vehicle, they would. It’s all a trade off. I’ve been driving versions of this calibration for a couple of months now, as a 2nd party guinea pig. Here’s what I see, good and not…
Benefits:
Fuel economy: Your results WILL vary. I’m driving half the distance I did daily last year (off road only). Logically, short trips hurt fuel economy. But I’ve gone from 21.1 to 23.5 mpg, an 11% improvement when I expected worse. I could get higher mileage if I drove more, but I only filled up once in the month of May.
Torque: The F37 torque is back, plus a lot more. Have a hankering for the smell of burning rubber again? It takes two feet and a will, but it can be done. Your butt will feel the difference.
Tailpipe smoke: Gone. Haven’t seen any. Big smiles – very happy.
Shudder: I had a ‘driveline’ shudder after a hard acceleration then backing off to maintain a steady speed. About three seconds later the bucking would start. I could get it in 1st, 3rd, and 4th gears. It wasn’t the torque converter, transmission, axle or drive shaft. It was the engine. That shudder is now gone. If I feel nostalgic, I can switch back to the old code and it comes back like turning on a light switch.
Intake manifold crud: Complete elimination of EGR means the blowby oil (for non EHM or Provent or other filtering solutions) doesn’t coke in the intake any more. My MAP sensor gets oily, but that doesn’t build up.
Risks:
Fuel economy: Machiavelli wrote that power corrupts. He was wrong, it is torque that corrupts. If you drive it like you stole it, you might smile more, but you’ll fill up more also. Maybe if I had ‘evaluated’ top end performance less my fuel economy (see benefits) would have been better. I admit I've had a bit of fun lately.
Torque: By now most of us have a pretty good idea that the original torque converter wasn’t really up to the task. That's why it was recalled. The post F37 torque converter is better for durability, worse for NVH. Is it up to the task of this additional torque? So far yes, I'm not slipping, but some sort of upgrade is quickly percolating to the top of my list as a preventative measure. Those who have already upgraded their torque converters can disregard this as a risk. The rest of the driveline (including the transmission) should be OK.
Tailpipe smoke: This is not a highway legal solution. CO2 goes down, PM goes down, NOx goes up. No way around that one. Those who have already abandoned EPA legality can disregard this as a risk.
Engine durability: Higher torque means higher stress on engine components. But when you bought your KJ, whether you knew it or not, you bought an engine calibration that had been tested to work under most imaginable conditions for the life of the vehicle. This calibration came from the same source, with the same attention to details, and access to software and diagnostic tools. When I was asked to try it out, I didn’t give it a second thought.
Other:
NVH: It has a little more diesel ‘bark’ in it taking off from a stop, some will not like that, some will smile more. It’s not like driving a jackhammer in my old 2001 Cummins HO, but you will turn more heads in a parking lot. At speed it’s the same as today.
Overall, some nice benefits not available anywhere else, some manageable risks, just like anything else in life.
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2005 CRD Limited Flame Red w/ Renegade rock rails & light bar, AirLift 1000. 225/75R16 MT/R's on cheap black steel wheels, dual MOPAR subwoofers, Ipod kit & seat covers, Samco hoses - totaled and gone. 2008 WK Laredo 3.0L diesel - AirLift 1000, wife won't let me mess with it much. 2013 JK Sahara on order.
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If not it would have been gone long ago before it got me killed 
