WDKUGDN is the throttle angle at a certain rpm where the throttle plate is no longer a restriction to air flowing into the intake mani.

I'm not sure if I understand it correctly, but this is why I did what I did.
Somebody please correct me if I am wrong, 'cause there is a good chance of that  

I added a few degrees to open it up a little because 12psi gates are going to be pushing more airflow through there than the stock 6psi gates.

The throttle is only opening to WDKUGDN in areas on the KFVPDKS maps that are <.95.
When you cross over into an area that is >=.95, the throttle blade sorta changes strategies and opens up more.

If you leave WDKUGDN stock with gates set higher, there will be a bit of air backing up behind the throttle blade that the ecu is not expecting.
When you cross over from a .94 area to a .95 area, the throttle is going to open and this extra air is going rush in unexpectedly.
You may feel this while slowly rolling into the pedal. When it crosses over, you might feel 1 quick surge as that air rushes in.

edit to reflect fr numbers instead of 551m

On my Jetta 1.8t F21, I've only tuned the KFVPDKS axis, and I have been very happy with those changes as it were.  After reading your description on what WDKUGDN does, I will go in and play with that a bit too.

But why use ambient for air density? Shouldn't the density be at wastegate cracking pressure?

I don't think that's right. PSPVKDUG = .95 so we're talking about a range of (.96-.95)/(1-.95) through 1, or 0.2  through 1.0, so i think it is more properly stated that it is proportional to where the map output lies between 0.95 and 1.0

OK, I think your description was enough of a kick in the butt to jar some brain cells loose and get this to click for me  

I'll use the values straight from the fr here to keep things consistent.
Will also make some of the other numbers up to keep the math easy.



Say we are at a pedal pos that req's a pr that puts us on a cell in KFVPDKS that is .95, and at 60% throttle (WDKUGDN at that rpm?).

The .95 in KFVPDKS being <= to PSPVDKUG(.95) means that the turbos can make the req pr on wg psi without any help from the n75.

I think the throttle will be at WDKUGDN here with no reason to open it anymore because it is not a restriction at this angle. It is allowing it to give everything it can on wg psi. (.95 is actually right where the throttle changes strategies, but the formula for the new strategy cancels itself out at this point)



Now, say we give a little more pedal, move to a higher req pr, and land on a .98 cell in KFVPDKS.

To make this new req pr (that is now above wg psi), the ecu needs to start feeding wgdc.

The throttle also needs to open a little more to stay out of the way of the increased amount of incoming air. That formula is how it does this smoothly on its way to 100%.
This is how it works, or at least my best guess anyway  
We were at 60% throttle. That leaves 40% remaining (on its way to 100%) as the Residual Throttle Value.
With the formula (.98-.95)/(1-.95), we get .6 (or 60%).
60% of our Residual Throttle Value (40%), is 24%.
Now we add that 24% to our original throttle value of 60% (WDKUGDN?), for a new target throttle of 84%

Sweet, this cleans it up a bit and should make it easier to find in a search.

If you still havent noticed, the 2.7 is .97, not .95 as in the fr.
Prob a good idea to use the fr numbers when we can to keep things consistent with the document, but something we need to keep in mind.

What I am trying to make go away is chirping/hooting at ~5psi when you are at a constant load that will hold the motor at a fairly steady rpm. Like going up a hill or something.

Playing with this stuff def seems to make the transition into boost much smoother and more controllable. I think I have it close enough that the throttle plate is steady and not what is causing it. The car drives and responds to pedal input almost as smoothly as stock anyway.

I am currently leaning toward what snowtrooper said about not asking more of the turbos than they can reasonably supply. We may just be asking too much of the turbos down low and pushing them into surge. They rip through just fine on a hammer down pull, but seems like they are just not able to sustain that amount of load in a steady state. But, as with pretty much everything I post here, Im not really sure if that is how it actually works 
Seems like its leaving a little on the table, but will pull ldrxn down a little and see if anything changes.

Here is a old pic.
I dont remember much about it, but the throttle blade was steady at first, and joined the party where you see it change toward the right side.

If nyet makes ecuxplot look like that I will kill someone.