there are NO adjustments that should be made on these unless you are carb certified and have direct factory support, in most cases even with factory support they replace the component generally.

if the injector is malfunctioning replace it...
if it continues to leak internally replace the injector housing...
if the throttle body is malfunctioning try cleaning it, if that does not work repair the wiring if damaged, or replace the unit.

there is not much with these components that are servicable, they are meant to be replaced if faulty.
if further damage occurs to the engine it's all on you if you go into any of these sealed components trying to repair them.

Liftdoctor, can you find out from your tech support contact if in fact the fuel trim was the value being looked at? Also, on the main injector where the wiring harness goes into the body, I see a very small set screw, which might be the lock, followed by a slotted & threaded screw in the center, is this the adjustment area? What fuel trim value should I be looking for? Thanks

Had this problem one time. It was the main injector. Their operations deteriorates over time. The tech support guy was able to determine this by looking at fuel trim values, I think. He recently told me this injector is adjustable. You must heat the end of the injector with a soldering iron to melt the thread lock, and adjust the set screw in the end of the injector. I have not done this, but it is worth a shot.

Is it possible to look down the throttle bore & see the throttle plate? I'd check to see if the throttle plate is moving while it's hunting. If it's starving for fuel, the rpm would begin to drop, then the throttle plate would open to compensate, etc.

Also- have you checked to see if the timing is steady while it's hunting- just a thought.

Were those parts OEM? Or TVH?
Also there was a mandatory injector housing swapout on those trucks for that excess fuel leakage problem. I would check with you local dealer and make sure it has been done.

To all that I have discussed with: hooked up a mechanical fuel psi gauge at vaporizor, psi was ok but let sit overnight and psi drained off by morning. Checked for external leaks-nothing. Pulled air horn off and found main injector dribbling fuel into intake, also assist injector had a broken spring, r/r both items, relearn throttle settings, etc., but is still surging/hunting at w.o.t. Wiggle tests on wires during the problem, no change?

surge/hunting occurs only at wide open throttle, but will not occur every time you go there? When it does happen, I will back out of full throttle SLIGHTLY and the engine runs fine again. Problem happens with no load or load. Watching the inputs on Diagnozer, throttle & accelerator % holds steady.

Does the hunting occur when engine is under load (such as in gear, dead headed tilts,etc) or no load? I'm assuming it hunts at the governed only or does it start hunting at some point on the way up to governed rpm?

ok since you do have diagnozer, set the communication settings for VCM1 to ECM, go to the input monitor tab, watch the LPG fuel pressures, they should run in the range of about 5000 (a little less or more)
if the ranges are higher then it is running too lean, if lower its too rich, if it is fluctuating badly it probably is an injector problem.
Also pay attention to the pedal position and throttle sensor readings
at full throttle they both should go to 100%. Any fluctuations in those readings will indicate a problem.

I did run the engine w/o air filter, but no change. I have diagnozer so will keep going. Did not remove the injector or other parts in that area, but will look at this morning, thanks.

ok that serial number range does fall within the Tier 1
since your alternator output is normal then forget that, was only a suggestion anyway based on what i found in the bulletins.

since you are only getting a surge during full throttle and no codes, have you tried cleaning out the injector body throat? Pull the injector and clean it with non-volitile cleaner like contact cleaner? pull the fuel sensor plate and clean out the last chance filter element?
Also just for posterity and thinking outside of the box.... Try running without the air filter to see if there is any restrictions due to a stopped up filter?

worst case scenario would be a mechanical issue in the throttle body?

I would suggest watching what is going on while this surge is happening on the laptop with the diagnozer program, might give you a better idea of what is going on, this may not be an option for you though, just a suggestion :o)

Swoop, Kevin & Edward, alternator is within range, serial # AT3504303. Oxygen sensor voltage is switching, but tends to run lean more often than not. Thanks

whats serial number?
need to determine what Tier level this truck is so we can determine what injector body it has. Early Tier 1 models had different injector body's , then there was a change at pre-tier 2 and several service grams had come out on this since then, even a mandatory injector body change out.
what edward and kevin suggested are certain possibilities of course :o)

Also....

I did come across a bulletin about engine surging above idle that deals with the alternator over charging and causing an over-current in the electrical system, this effects the fuel system components as well as other components.

Check the alternator output, make sure it is within the range of 13.8 to 14.9v , if any higher then the chassis and engine block ground should be checked and repaired, then recheck the output.
The volt drop test from battery to chassis and battery to block should not exceed 0.5v.
If problem persists then the alternator should be repaired or replaced.

forgot to mention the crank time is normal

Kevin & Edward, fuel psi running at 5psi. You can run the accelerator w.o.t several times without any surge, but when it starts to surge it will not stop until you release from full speed and accelerate again. This is happening without loading the engine down into hydraulic tilt by-pass, so the assist injector could still be acting up? Thanks guys

my money would be the assistant injector, and would swap one from a known good unit for testing, but what they said above is right on.

Does this truck have a longer than normal crank time when its first started???
If the A/F ratio is going high,possible causes are intake air temp sensor......MAF sensor...is it dirty??? Can you check O2 sensor and see if it is switching back and forth??
Another possibility is the assistant injector leaking or not working properly as well as main injector issue....or a pressure relief valve in the injector holder is sticking open some.....with the engine off and key on do you hear fuel going thru injector and intake and going past relief valve......there are two relief valves in the injector holder...might be good idea to remove injector holder remove main and assistant injectors and clean the injector holder of gum and tar...also check fuel PSI...should run around 4.5-5 PSI