The IDM mod has a little bit of effect on a stock truck with no aftermarket calibrations from a programmer or chip. Some folks can really feel a difference, but usually they are in the 95-97 model year crowd. There are great write-ups that Jonathan and Dave of Swamps Diesel Performance have put up over at Powerstroke Nation about how and what the IDM is doing after modification. "golfer" is Dave and "Swamp" is Jonathan.
IDM?? - Powerstroke Nation
Swamp's Hi-Voltage / Hi-Frequency IDMs - Powerstroke Nation
7.3 Power Stroke IDM
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Originally Posted by Colt
Obviously in the lower RPM ranges you'll have more time to inject a certain amount of fuel, the more RPM's your running, the less time you'd have..
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Which is why a lot of 7.3L trucks are not competitive. Here is a list of available pulse width times (this is only from an electronic standpoint, not including the mechanical lag inherent in the injector design that hovers around half of a millisecond or more).
750 19.22
850 16.85
950 15
1050 13.5
1150 12.2
1250 11.2
1350 10.3
1450 9.5
1550 8.9
1650 8.3
1750 7.8
1850 7.4
1950 6.9
2050 6.5
2150 6.15
2250 5.85
2350 5.55
2450 5.25
2550 5.25
2650 5.05
2750 4.7
2850 4.45
2950 4.35
3050 4.1
3150 3.95
3250 3.84
3350 3.7
3450 3.6
3550 3.45
3650 3.35
3750 3.23
3850 3.12
3950 3.08
4050 2.9
4150 2.82
4250 2.71
4350 2.6
4450 2.55
4550 2.5
4650 2.45
The above values are why anybody that wants/needs to make big power (higher RPM) uses huge nozzles. There is very little time to inject the needed fuel once you get above 3000 RPM, and larger nozzles are the only way to get the fuel out in that short amount of time.
With any aftermarket calibration, the start of injection (timing) is already advanced by any number of a few methods. There's nothing to compensate for while running a 140V IDM, nor will you see much if any benefit either way while running aftermarket programming.
As far as the whole fuel/"timing" thing goes, you can forget some of the stuff you've learned about a gasser. Too much fuel down low will "snuff out" the turbocharger and you will not get fast spool-up. The same goes with the start of injection; by advancing the "timing", more heat is retained in the cylinder which can slightly delay spool-up. It's good for fuel efficiency and performance once the turbo "lights", but given two identical calibrations but running one with a global offset of a few degrees of retard (from calculated total advance) usually results in faster spool-up due to more exhaust heat being introduced to the turbine inlet.