Hi Tim,
First thing I would like to say is I know how difficult it is getting a mechanic, but I would advise you to get somebody to give you a hand, doesn't have to be an expert, just some experience. For the timing it really helps.
All timing of stick speeds are done at high idle (full rpm) start the stick fully retracted (near cab) and extend all the way. I tell the techs in the shop to use their timer on the phone or a digital stopwatch, i can check tomorrow what the time should be, think it's under 3 seconds. I would practice doing that a few times, you get a feel of the machine when it hits the end (try it with your eyes closed) that way when you are timing, look at the timer, not the stick. Repeat a few times and you should be pretty close. Jot the numbers down (ain't written, never happened)
Reason for this, gives you a base line. Compare the timing before and after adjusting to see the difference. (stick out)
If adjusting the 1 pump doesn't make the stick slow by 1/4 to 1/2 second, adjust the other pump and re-time again.
What you are adjusting is the torque curve of the pumps. Adjusting exactly how I said, shortens the curve, pump de-strokes (unloads) earlier.
I believe what is happening is that your pump is not de-stroking when the pressures rise, putting added load on the engine (black smoke) This is a common problem I find with Daewoo/Doosan excavators when they get older.
Having said all that, the final test would be to push the machine around with the stick out.
If that doesn't take care of it, the servo spool is likely stuck/hung up in the pump regulator. DON'T try to repair that without an expert doing it. The potential is, small problem turns into a big expensive problem.
Have 2 225 Solar V's in the area, both over 15000 hours, did this procedure on both of them, with the same issue.
took a half day to convince the customer to not rebuild the engine on the first one. Time on stick out was just around 2 .5 seconds. The next spring he phoned and said "come out an' do that voodoo thang again"
Sorry about the long post, and good luck with your machine, please let me know how it turns out.
I will happily provide any other info you need.