Every actuator has a minimum lift off pressure. This is the least boost u can ever run on that actuator. Std is 4psi, -31 7/8 psi, -34 around 14psi. These figures vary slightly.
You can increase the boost by shortening the rod. When you shorten the rod, u tend to reduce lag due to preventing wastegate creep. This is because the engine can boost a little more before the wastegate starts to open. You feel this in the car as the power coming in harder. So, generally it's good to run more tension/shorter rod. You can only go so far, as if u keep shortening, the wastegate won't open enough and u get boost creep - ie boost rising with rpm in the higher gears.
The amal valve serves 2 purposes. It goes inline with the boost feed to the actuator. WHen it is open, it bleeds off pressure - fooling the acuator so that it doesn't see the full boost the turbo is developing. The wastegate then opens later.
Say u have a std actuator, which opens at 4psi, and then u have an amal valve which bleeds off 50% of this pressure. When the turbo is developing 4psi, the actuator only sees 2psi, as half the pressure is going out through the amal valve. As the lift off pressure is 4psi, the actautor doesn't move, the wastegate stays shut, and the boost continues to build.
When the turbo is producing 8psi, half this will be bled off, so the actuator sees 4psi. This is it's lift off pressure, so the wastegate opens. This is exactly what happens on a std car - hence they run around 7-8psi.
The second thing the amal does, is a safety cut. By having the ECU control the amal, it can close it off in certain conditions - namely when temperature goes too high, or it detects knock. By closing the valve, a std car will revert back to wastegate lift off pressure - ie 4psi. In honesty, this feature isn't needed - u should keep an eye on ur gauges, and if things are getting hot then you should be off the throttle...
Now, if you fit a -31 with a lift off pressure of 7psi, and run the amal, u may boost at say 11psi, with the rod in it's longest position. Now, i say may as it depends on how the amal valve is jetted. I said before, that the amal bleeds off 50% pressure. That is a rough approximation, and varies greatly. You adjust the amount of bleed by jetting the amal valve. All this means is you fit different sized restrictors in the bleed port of the valve. As you can imagine, this is trial and error and a bit tedious.
Say you fit your -31, with the amal still in place, and it boosts at 11psi. Running upto around 18 psi is easy - just shorten the rod and job done.
But, what happens if you fit the new actuator and it boosts at 15psi? And you want to run 12psi? Well first, unplug the amal and see what it boosts at. Whatever it is, this is the lowest boost you can run with that actuator.
You can now start rejetting the amal - put a bigger restirictor in the bleed port to reduce the boost. Personally i wouldn't, as it's a ballache. This is where a bleed valve comes in. A bleed valve (3 port type) goes in place of the amal valve. It serves the same purpose, but is very easily adjustable. This is a good thing for tuners. But, it has undeservedly given bleed valves a bad name. It is easy to unscrew the bleed valve, the boost goes sky high, and so does ur engine. Simple cure - don't fiddle with it once set, and ur engine will be fine.
Fit the valve, and make sure it is in its fully closed position. Do a test run, and if you want more boost, greadually open the valve. Turn it max of 1/8th of a turn and then test until you get the desired boost and lock it in place.
Job done
