Much to check;
Dipstick o-ring replaced
EVAP tubing this would be the line runnning from the rear of the car to the back of the valve cover, through it, and out the front, right?
Brake Booster and tubing just replaced the tubing, but not the booster. Smoke test will show if it's the problem.
Intake connections including the MAF to intake seal all tight.
Boost to throttle body connections if you're referring to the charge pipe that connects to the throttle body then it's tight.
Intake manifold for cracks is there a common failure point on these?
Do you notice oil seepage anywhere? Seal those connections or replace damaged tubing VW tech said there was some on the belly pan, but not sure where it's coming from.
Have it smoke or pressure tested if all else fails to find it. once DSG is in I'll be doing this.
It is possible it is only a leak...but I think yours may also be poor fuel delivery by injectors or the MAF.
Reading this helps explain how a leak usually doesn't affect "partial/off idle" as it does at idle and stft. http://wiki.ross-tech.com/wiki/index.php/Fuel_Trim_Info
The injectors are OEM new. So is the MAF. Both replaced this year.
Based on your partial and idle comment it sounds like I have both then. STFT shoots to +25% after clearing codes and the LTFT partial is high. It doesn't fluctuate as much anymore. Hanging between +13.28 and low +14.
See above in red.
I'll also add that removing the leaking oil cap neck from the valve cover brought the LTFT partial down by 5-6%. Makes me wonder if the channels inside the cover are falling apart too like yours did. If I smoke tested through the rear breather tube or evap port and saw smoke coming out of the oil fill on the valve cover that would indicate there's a problem, right?