With the turbo deisel it is easy to add more power, but don't believe the big MPG claims.
If you go off the overhead MPG display it will show a MPG increase with the chips because it dosen't know your adding additional fuel, but if you hand calculate the mialage you may see 1-2 MPG increase in the economy mode.

I have a friend who just traded his '06 for an '08 and he may be selling the Edge Juice that was on the '06. If your interested, I will see if he still has it and how much he wants to sell it for.

I have a '05 Quad Cab, Long bed that has the Edge Hot Juice, AFE stage II intake, Magnaflow 5" exhaust, banks technicooler/high-ram intake system, and Superchips/MSD Digital Propane Ingection on my truck. Just about all these products claimed mialage and power increases.
I don't think the intake or exhaust stuff made any difference in mialage, they may have been good for a few HP?, but they do help reduce EGT temps. On the other hand they made the truck really loud. In town, unloaded it is tolorable, but at highway speeds and towing the turbo wistle and Exhaust drone gets annoying really fast.

Make sure to have an EGT gauge to monitor temps because the chips/tuners can really boost the exhaust temps. One feature of the Edge Juice is that it monitors the EGT temp and de-fuels if they get too hot. It also monitors for transmission slippage.
As for the Propane system, I just got it about two months ago and when programmed for the lower settings, it does help fuel mialage to where I may be saving $0.01 to $0.02 per mile in overall fuel costs, but the system was about $1500 with the tank, lines, and computer/regulator, so the break even point to where I will actually save money is after 60,000+ miles (depending on the price differential between Diesel and Propane.)