[Diesel_Dave]

Unfortunately for me, there is no BSFC for my engine... it is not stock, nor are the programs I run on it.

Yes, you're right about that. Cummins doesn't release BSFC maps publically for proprietary reasons. That being said, you don't have to know what the BSFC map is for P&G to work. Most BSFC maps for modern turbo-diesel engines have more-or-less the same basic shape. Of course there are differences but the general shape is what allows P&G to be effective--principally the fact that the engine is far more efficient at high loads than at load loads. Same goes for non-stock programs--you're not going to change the overall shape of the BSFC map significantly with a program.

Everything on the intake/exhaust sides of the engine is not stock, and with extra air comes a need for extra discipline (or, the "nanny mode").

Assuming your turbo is still stock, I don't think your intake & exhaust mods will have a huge effect on the air flow until you're running up near max power. When your flows are low, it's not going to make very much difference. I can see how your intake and exhaust mods would have an impact on the max power of your engine, but personally I don't see it having a huge effect on things when you're dring for FE (when your air flows will be relatively low most of the time because your rpm's will be low).

On the eco program, though, there is very little rhyme or reason to its behavior. Keep in mind, this program wasn't designed to be eco, I just use it as my nanny to keep me within more efficient ranges of operation.

I'm not sure where you got this "eco" program but, honestly, it doesn't sound that great to me. From what you're describing I think you'd be better off just sticking with the stock program. Maybe add a little timing and/or rail pressure to it, but that's about all. Sounds like the program messes with the transient response. You probably want that for your "fun" program, but you won't need it for FE. Sounds to me like this is why you're having smoke issues. Remember that smoke is primarily from running a low air-fuel ratio. If you're sending in too much fuel before the air is there you'll get more power (because more fuel is burned), but that fuel won't be burned as efficiently (smoke is unburned fuel). Advancing the timing and increasing the rail pressure will generally reduce smoke and help FE, so I'm guessing you're problem is air-fuel ratio. Since you have a 5.9L engine, it was designed to run quite low smoke without a DPF-several times lower than the visible smoke limit. Something about your program is increasing smoke relative to stock. My guess would be it's low air-fuel ratio. Either that or your timing is just way, way too advanced. That can give you smoke too, and hurt your FE.

When you P&G, it sounds like you may also be pulsing a bit to hard as well. The other day I timed myself on a level stretch of road with no traffic. I pulsed from 27 mph to 50 mph (all in 6th gear) in about 12 seconds. My glide back down to 27 mph took about 1 min 10 sec. That gives you some idea of how I do it. I'm not claiming that my way is the absolute best way, but that's what I do and it works for me. You might want to give it a shot and see what happens. You might have to slow your pulse down slightly because you have a 5.9L which has a wastegate turbo, as opposed to the VG turbo I have in my 6.7L--it might not spool up quite as fast.

Hope that helps...