Turbo problem, new clues

2000 Beetle TDI, stage ll chip (tuned by someone from Kerma at a TDI rally in Portland, OR), .205 injectors. It has been a couple of years now that I have had turbo problems and I can't figure out what is going on. I have cleaned my snow screen, have a new N75, checked, with a mityvac, and replace all my vacuum lines, changed my turbo actuator, cleaned the EGR system and still get smoke under load, new MAF, air filter, fuel filter and I keep losing my turbo under load. It seems to be worse the hotter the engine and outside temperature is.

My latest test was to remove the vacuum line from the actuator from the N75 straight to the vacuum source. This is supposed to by-pass the MAF and N75. The turbo still quit. And by the way while driving I just cycle the key off then on real quick and the turbo comes back and has full power until I put it under load and it quits again. Is there an over boost sensor or is my injection pump going bad? My first injection pump blew up, then my new from VW dealer injection pump could not keep the timing. By the time I figured out it was a bad brand new injection pump, the warranty ran out. Whitedog lent me a spare which is what I am using until I can afford to rebuild the VW sourced pump. Anything I missed?

Do a search on "limp mode".

limp mode

Could be a number of things. If you follow the link in my signature, the first thing you will see is Canadiangrizzly's link to systematicly diagnose your problem. When you put in the larger nozzles, did you have them pop tested? You may be overfueling, causing the black smoke, greater chance of carboning up your turbo, also greater chance of exceeding boost limits- which will make the computer go to limp mode.
Do you have a boost gauge?

I am working on my car at this moment and will try system test as suggested. I'll be back to let you know what the results are.