Thank you for coming back on here and responding....I was curious if you had ever decided to upgrade the WG or at least have it inspected.
I know about having an unexplainable issue...where you have to replace $#!@t in a process of elimination. I still haven't sorted out why my fuel rail pressure only specifies 110 bar when it should be 140 bar. After more than two years of digging and working with GIAC, nothing. I can only assume, because I went from GIAC to DriverMotorsport(DM) to GIAC again. When I was using the DM tune, I did a couple of swaps. One being I added a Forge WG Actuator for the K04 because their tune was at 26 PSI and the stock WG Actuator was having trouble staying closed so to build the boost when added preload didn't help. The other was I went catless. So those two are my focus now. I plan to get a new K04 turbo and that will have the oem actuator...and then I am going to get another catted DP.
Anyhow, I was trying to help someone with a similar issue to yours. He recently had his 2006 GTI (w/K03) tuned, but it only boosts to 17 psi and tapers down to 10 psi. Still working with him and he says there are no leaks and the DV and N75 have been replaced. But I have yet to see his boost data which he promised soon. I am leaning on it being the WG is loose to not seal when shut, the WG actuator spring is not strong enough or it needs more preload.
Sad to hear yours has been on a rough road as of late...hope you have a pick-me-up soon. Mine is luckily been able to be driven less...approximately 2500 miles per year and it is still being garaged...but it is looking to need near $4000usd in parts soon. It's a long list.
This was a month ago...can't believe I have had it for near 13 years now.