P0299 fault on TT tdi dilemma...

[stephngaz]

Hi folks,

My wife's 2010 TT tdi has been suffering the dreaded P0299, limp mode fault but all efforts are coming to no avail.
After having the turbo off and cleaned (nightmare!!!) found the vnt actuator to near dead so was replaced with new Audi spare which I set up using vcds and mityvac.
I also checked the n75 solenoid using "Basic Settings" test and it moves freely with 0-20" vac when cycling on/off. Plus the exhaust changes hopefully confining the vanes are actually moving.
Problem is i have near zero boost and limp mode cuts in after 200 yards.
The "turbo" graph looks like this:
32369

I'm just hoping there's someone out there interpret the graph for me. Looks like no boost from turbo or no reading.
I'm fairly confident on all motor issues but this one is killing me and I'm sure I missing the obvious...
It's a 2.0 cbbb engine with 72k miles.
Just donning the coveralls to go back under again!!!

Anybody help??

[stephngaz]

http://i1248.photobucket.com/albums/hh498/garymcluckie/image_zpsbgtg9s5z.png (http://s1248.photobucket.com/user/garymcluckie/media/image_zpsbgtg9s5z.png.html)

[stephngaz]

Well folks,
Still having issues with the TT.
Turbo has been off, cleaned and refitted. New vnt actuator fitted and setup with mityvac and seems to work fine, it starts moving at 2" vac and on the stop screw at 15". Voltage reading on vcds varies between 3.7v and 1.2v during actuator movement.
All the vac hoses inspected and no issues, plus the whole intake pipe work been tested for leaks with no issues.
DPF checked with vcds and results were fine with minimal sooting.
I checked the n75 solenoid with vcds test and also mityvac and results weren't convincing. Vcds test show the vnt actuator moving but it did seems a little slow to react as I thought it might bang open/bang shut but moved smoothly in about 1.5 secs in each direction. Vac test was garbage in my mind as it seems a poor design and hardly holds vac unless the outlet and atmo port are plugged, even then it still bleeds off.
I took the car for test drive and almost instantly go into limp mode, so stopped the car, engine off and disconnected vnt vac hose. The short drive home and the car felt great, power and speed but nota long run cos scared of blowing it up and over boosting.
Does anyone have an idea how to test this n75 solenoid properly before I go buy a new one.