What happens when you turn the 5/32" allen screw in more than half way? Is more fuel/power to be had?

When the pump was built, the Roller to roller dimension was set by adjusting the leaf spring screw you are referring to, to Stanadyne's specs to achieve desired fuel delivery. The further you turn the screw in, the more the leaf spring allows the rollers to go and pump more fuel.

Since I'm not seeing a cloud of smoke pour out the tailpipe, I'd like to go further in. The 1/2 turn only seems like it's slightly more fuel. What would you suggest as a next step. another 1/4 turn in?

http://www.realdiesel.com/images/db2pump_010.jpgHere's a picture of the Rotor, you can just see the side of the screw, the leaf spring is underneath it, the plungers/shoes/rollers are absent but maybe this will give you an idea what this screw does.

i understand what this one does what does the allen screw in the end where the fuel inlet is do ?

Thats the transfer pressure adjustment, Clockwise turns the screw in and puts more pressure on the regulator piston and increases pressure, CC decreases pressure.

What is the stock DB-2 transfer pressure? Isn't this the pump that can lock up if turned up too much?

Transfer Pressure increases with RPM 125psi MAX at full RPM, yes you can sieze the head so don't go in there and change it more than 1/4 turn.

My 4911 pump is turned up all the way, egt's are still controlable too...

A good percentage of original DB2-4911 pumps we see come in the shop have low fuel outputs. The settings appear right, it's just the head no longer puts out enough. I would suggest this might be your dilemma also. You just have an old pump and your bumping the delivery up just made up for wear. Your next turn of the screw will show an increase you can see, I am sure.
As for setting the pressure up don't do it! I turned a 4911 RPM's up the other day and around 3,900 rpms or so the pressure had spiked to 125 psi. The head can seize at that pressure. So if you turn the RPM's up you will be in the danger zone. Any RPM increase higher than that will need to be done on a test stand with a pro who knows what he is doing.

Any RPM increase higher than that will need to be done on a test stand with a pro who knows what he is doing.Would be a DieselPro or a Diesel-Pro, LOL ;)

He's right, a 4911 pump is a very different animal than a DS, head siezures are practially unheard of in DS pumps, (I've only seen one, caused by gasoline) but it is a very real and expensive concern in DB2s. An experienced technician will be able to safely calibrate the pump to achieve the RPM and fuel delivery you want on a test stand. I also concur, that high percentage of 4911 complaints are low power from low fuel delivery.

Bill Heath of Heath Diesel sent me a printout of how to correctly adjust the fuel pressure with increased boost after installing his TurboMaster. You could contact him as he is extremely knowledgeable or I can copy it into my computer and send it if you want me to. I haven't done it yet since I am in Northern Michigan/Canada now and it's too cold to work outside on my truck unless absolutely necessary.