Wow, it always amazed me the differences in performance from vehicle to vehicle with the supposed same modifications.
Here is my experience:
SETUP: I have the EZ box and the 275 injectors. The EZ box is set on level 3 ALL THE TIME

(Did many experiments with setting #2 though)
SMOKE: very little. The only smoke I get is when I really nail it at low boost, it puffs for about 2 seconds, and that's it. Once the boost comes up, it is clean as can be. I don't understand why some people see so much smoke. I don't.
EGT: The absolute MAX that I have EVER seen with setting #3 and the 275's is about 1190 degrees. Even that was rare instances. For the most part, it is around 1100 max. Again, don't understand that one post saw high EGT's. Many vendors recommend this as a "safe-EGT" combination for towing.
USE: I tow a 9000 lb fiver, and just returned from a second 800 mile trip with this combination of mods. It works.
CAUTION: Your stock clutch will not tolerate much more power than what this combination puts out when you are towing heavy. I even worry about the transmission at this power level towing, as it makes a whole lot more groaning, vibrating sounds than it used to with stock power levels.
FUEL ECONOMY: If you drive 70MPH or higher when towing, setting #3 seems to affect MPG adversely. Not a lot, but some.
If you drive at 55MPH, setting #3 will improve economy by 1MPG.
IMHO, the 275's and the EZ are almost the ideal combination.
But seriously, if you go any more, you need to think about the clutch. Empty, maybe not, but towing, I guarantee you it will be on your mind every time you tow.
My . 02
Shawn