I still can't figure out how to properly search the forums so if someone wants to move this to a place more appropriate, have at it. I wanted to inform the greater audience of my experience with a tuner. I have wanted one for a long time but have been terrified about sacrificing reliability or drivability.

My setup
2005 Excursion with ~240,000 miles.
165cc injectors (30cc over stock) with stock nozzles
Coolant filter (really does work and has pulled out garbage consistently for 4 years)
Bulletproofed EGR system still intact, but EGR valve has been intentionally broken for 4 years
285/75R16 tires that are basically 33"
Rough Country front leveling kit so I could fit a dual stabilizer (link)
3.73 gears
Everything else is bone stock, no headstuds
I monitor everything from a bluetooth OBD2 transmitter to OBDLink MX which gives me pretty much everything I need and nothing went out of parameters although I've never done data logging to look for anything small. I just watch its gauges while driving.

I drive pretty conservatively and average about 14.5mpg. When I'm on the highway doing long distances (time is money) I get about 13.5mpg. I have a little notebook that stays in the truck for fuel and maintenance logging and everything is hand calculated. I do have the 44 gallon tank and every refill is OVERFILLED until I have diesel literally sitting at the cap because I like consistency.

I make regular trips from the Austin area to the Atlanta area which is about 890 miles. I take about 250 miles of state highways in east Texas that have a lot of harsh hills. Test trip before the tuner set at 65mph and letting cruise control simply power through the hills yielded 13.8mpg when combined with I-20 travel over 601.2 miles. Next, testing was done in the extreme setting which has the most power and the best chance for overall mpg increases. With tuner installed on the exact same route, speed and cruise control I averaged 18.82mpg over 804.8 miles (same hills, same interstate). Net increase of 5.02mpg! Driving the hills without cruise control would have probably netted over 20mpg.

If you have a 44 gallon tank and want some range estimates driving unloaded, here's mine. Keep in mind that I tip the scales at 8900lbs. I have drained all fuel in the tank (not the lines) and found that at overfill I hold 48.1 gallons and that is when the diesel is sitting at the cap.
123.2 miles until I hit 43.6 gallons remaining (OBDLink only reads my full tank at 43.7 gallons)
Centered on full was 142.0 miles at 41.2 gallons.
3/4 tank 212.1 miles at 34.3 gallons
1/2 tank 433.1 miles at 22.0 gallons
1/4 tank 643.2 miles at 10.4 gallons
100 miles at 43.7 gallons
200 miles at 38.1 gallons
300 miles at 31.0 gallons
400 miles at 24.2 gallons
500 miles at 18.3 gallons
600 miles at 12.6 gallons
700 miles at 7.1 gallons
800 miles at 0.7 gallons
When I refilled at 804.8 miles I still had 2.1 gallons in the tank apparently.
*Yes, it pisses me off to no end that the numbers don't drop steadily in a nice linear fashion....212 miles between 3/4 and 1/2 tank but only 70 miles between full and 3/4? Really? I can only assume that it's due to the fact that I currently have 2 blown shocks and was just shaking the fuel sender level too much? The biggest discrepancy WAS during the hilly portion though /shrug. The interstate portion was pretty consistent.

On the flattest parts of the interstate I did try to check OBDLINK for mileage estimates. It said that at 60mph I was getting ~26mpg, 65mph was ~22mpg and 70 was 18mpg. Those were just looking at the instantaneous numbers, but with hills factored in the 22mpg seems close-ish for flat ground. Next time I do this trip I might set it at 70 for the duration just to see.

I split the return trip and drove normal (for me) in order to get the time versus money analysis. Over 432.6 miles I didn't get passed...I did not drive under 80mph and I'd say close to a hundred miles at 90mph. I averaged 16.80mpg which is still an increase of 3.3mpg. I did a time analysis that showed my average speed was 83.6mph...think about that for a minute. On the 2nd leg I drove even harder through East Texas passing non-stop on 2 lane roads pushing 100mpg while passing and averaging about 85mph the whole way over 270 miles and got 14.85mpg.

I bought this tuner for mpg gains on the highway and I am not disappointed in the slightest. Cruise control usage used to kick out of overdrive on hills, not anymore...it just commands more boost to power through. Releasing cruise control used to have a harsh drop in speed that would throw you forward in your seat, that's gone. I have power for DAYS at any speed without any sort of lag including at stupidly high speeds. I used to have issues merging onto interstate ramps from low speeds, now I merge like I'm in a mustang thanks to the acceleration. There is zero smoke except for the hardest of accelerations at all speeds and really only from a standstill while the turbo gets rolling. If you want it, you can seriously smoke the tires... I tried to turn into traffic in an absolutely horrible spot in Austin where the gaps are really small. I got tired of waiting, floored it and threw an enormous cloud of smoke while sliding sideways across 5 lanes like I was on a 4 wheeler in mud Tokyo drift style. Again, this is a heavy Excursion... The only thing I don't like about the tuning is shifting into overdrive which is always rough now, but I understand that higher line pressure is needed for the extra power. All other shifting is still pretty soft. Under heavy acceleration the overdrive shift isn't even noticeable.

If you want a tuner but are worried about reliability problems like I have been for years, rest assured that these tunes worked out just fine. The tunes were from Tony and came from Total Diesel Performance on an SCT7015. Based on a total price of $510.65 with shipping and average price of diesel for my trips being average $4.80 I only need to drive 9,175 miles like a moron and it pays for itself. Driving conservatively only requires about 7,100 miles and this trip was 1,944 miles.

I don't plan to dyno the truck so these are just guesses. Stock is 325hp/570tq. -15% for losses should be around 276/485 stock. Tuned stock without headstuds/injectors/turbo/fuel systems have averages reported around 400/720. No idea where my 165cc injectors fit in here, maybe 440-450? Either way, I've got at least an extra 100hp and you can definitely feel it.

Seriously, if this is my increase then surely guys with tamer setups or a lighter foot can probably do better. I'm just going to settle down after this trip and push as far over 20mpg as I can for the next 800-900 miles. Haven't towed with it yet, but if I do I'll log and post numbers in the tow tune because I'm not brave enough to risk the EGTs in the extreme setting.