P0299 insufficent boost

Loss of power occurred a couple weeks ago. I inspected all charge hoses and connections yesterday, found normal oil seepage at joints, turbo has been always very quiet in this car, but its definitely operating. VNT moves through full range. Could this be something as stupid as a clogged ail filter not passing enough air? I haven't changed it for 40k but am going to this morning. n75 seems to be operating normally. Only code relating to this is P0299. Has anyone experienced anything like this? Cam is good, geared bsm.

I had sort of similar situation recently. Turned out to be a missing O ring on the turbo outlet. Either blew out or I did something awkward when I put the original patched hose back in place of a blown chinesium one. Point is, I never heard or saw any leakage and didn't find it until I did a pressure test on the charge air circuit.

Thanks Scubanero. So far I found the air filter was clogged to the extent it bowed upward about an inch up actually ripping across the pleats . I recently had changed the turbo hose with an extra I had and made sure all the o rings were fresh viton ones. Reset codes and took it for a drive, with vcds graphing boost. Performed like normal, then the graph line suddenly dropped and it went back to poor performance as it has been. The 3 or 4mm hase on n75 close to rad is oily and could be bad where it makes a loop, or could I be dealing with a bad n75 as some others here have. At least today I saw full normal power for a couple miles, so I guess I'm close to finding the culprit. Anyone have any ideas?

N75 could be bad. Also check the wires in the plug that goes to the N75. I recently had one were the connections inside the plug pushed up and barely made contact with the spades inside the N75 plug.

Thanks vwztips. I'll check that as well. that area is rather oily probably from before I clamped the breather hose. Its not that the n75 is expensive, its that it looks like a pain to change. Its annoying at best to get the teaser of full boost and not yet finding and fixing the gremlin.

Really not hard. Remove 2 10mm nuts and unplug the vacuum lines. It is somewhat of a blind operation though

Does it smoke more than before? If yes - check again hoses you might be losing air. I had something like that - the culprit turned out to be cracked elbow pipe (the one right after the air filter box), but mine was smoking and I was clearly hearing hissing noise for some time.
Friend of mine had similar loss of power and all hoses and everything looked good. No excessive smoke either. Got perfectly fine after replacing the fuel and the air filters.

Conclusion, N75 was not closing, which resulted in boost just after cold start, then low boost. Replaced N75 and full boost has returned, running better than it has in a long time. Replaced fuel filter as well but that was not the problem.