I am just taking this right off the site that nevrenufhp put on his post at the top of this page, so here ya' go:
On the back of the pump is a cover/plate that is said to be almost heart shaped(the AFC housing). There are 2 allen head screws behind that plate that have 3/8 (on B&C's pumps, a single 7/16 on the A) locknuts on them. On an 'A' model you can just take the screw out, since it cant flow enough to cause any harm. Carefully loosen the locknuts with a deep socket, then remove ratchet and insert the allen wrench through the socket so you can hold the locknut in one place. Turn both screws EXACTLY the same amount of turns. Usually start by going 1 full turn on both, then run it. Any additional turns afterwards should be no more than half. Don't get greedy, you'll burn it up. You can get well over 500Hp playing with those B model pumps, but don't come back here blaming me if you don't know how to take your foot out of it and let it cool down. With the screws were turned all the way out, and a C model turbo on it, you can get a little over 600Hp. But it gets hot, if not careful.
Here is the "springs method" for the 3406B&C. Much better results than the one mentioned above:
Take the line and 2) 1/4" bolt cover off the air fuel ratio on the very back and top of the gov. Nothing there to be scared of. Grab the plunger stem with plyers and break the 7/16" jam nut loose with box end wrench, Turn screw all the way in until just leaving enough threads to lock down. Not real precision, just set it anywhere tight. Re-assemble... On the very bottom of the rear of the gov. towards the outside (frame side) is another 1" tall 1/4" bolt cover. Remove the bolts, one on top of the other this time, and smack down on the cover with a screwdriver and hammer. The harder the better. It'll leave the gasket perfectly intact for reassembly that way. Again, nothin to screw up so have at it. Facing in from the back stick your pinky in the slotted hole and push in on that thing. Just face the front of the truck, turn palm up and stick it in. Again, and just to clarify, this is all idiot proof and you can't mess anything up on any of this. Ain't rocket science, for real. Easiest motor to jack up, for sure. SSSooooo, you'll feel the rack screw bar with the fuel and torque screws. Just push on whatever you run into in there. The more travel, the more servo movement. All you're doing with your finger is makin sure another bonehead wasn't in the playin. Make sure when you push it all the way in (about 5/16" travel plus change is about 425hp stock, but doesn't really matter how fat it does go) you can feel about .030" or so (just picture a .030" gauge and guess, really) of secondary spring pressure. That is the torque spring on the stop bar. It doesn't have to be exactly anything, just want that little bit of extra pressure for torque rise. I won't explain it all, but your feeling torque spring pressure from the screw making sure someone before didn't turn one screw out from the other (doing it wrong). There are two screws side by side. If there is no pressure there, turn the outer most screw (towards you) in until there is. Do this with a 1/4" drive 3/8" deep socket (12 point is easier) with baby vice grips clamped to the very end as the lever and a sumthin stupid like 7/64" or somethin allen wrench down the center. Just take your allen set and stick it in the end of the screw to find the size (or call your local dealer, ask for truck shop and just ask em what size). Insert socket, break loose counter clockwise with allen wrench in hole, turn screw and lock back down. If your torque pressure feels OK, or you reset it as stated, back out both screws evenly to the tune of about 20hp per turn or so. Wipe off housing and cover and stick back on with original gasket. No glues on anything anywhere here. If the trucks in good shape, go 3 turns or so and run it a round. If your pyro stays below 950, meaning it's timed close enough to stock or advanced properly, turn it out another 3 and call her good. That's it. Have fun. It can be super tweaked with meter timing and gov. removal, but you'll be pretty happy like this unless you run into me on the road somewhere. Want peace of mind and better mileage, take it to someone trustworthy (Cat dealer, and tellem you want an old timer on it) and set a tight overhead ($225 or so) and meter time ($100) to (for your 92) 17.5 degrees at 1000 and start at 1230, plus remove the stop screw and toss it. This won't make sense to you but that's exactly what you tell him. He'll know just what you're saying, believe me. That'll land you between 5.2 and 5.7mpg depending on what you haul, and between 530 and 560 hp. You'll know it all worked when it goes from 20psi boost to 27 the first time (3 turns) and 32+ the next (3 turns). Add an 0R6051 turbo for a couple more pounds and better power ($1000 with your core as an even swap, and don't let them try to tell you there's a core charge. There isn't, for sure). And don't worry, it'll all take it just fine. With more exagurated tuning, she'd pull 800hp just as it sits with no motor mods whatsoever and live to 750,000 miles without a hitch. If you're running 15psi boost right now and the first 3 turns didn't increase the boost, have the dealer replace you air fuel ratio diaphram ($100). Have fun... Thanks again to Tony from Welch Diesel Repair for this article!
But I am sure Tony will comment here to help ya' irregardless of what I put on here, and I would listen to what he says over what I say