You might be better finding someone local with VCDS to have a scan of your ECU and see or find a good independent garage, the dealers aren't the best for diagnostics as they're just trained fitters and not mechanics.
2 main points worth checking, don't know if they'll be related, but you'll want to review your diverter valve (DV) and your pressure control valve (PCV).
The PCV is easy enough, with the engine running at idle, remove the dipstick quickly (but don't leave it out for more than a second or two). If the engine tries to stall, the PCV is fine but if it continues to idle at normal revs, the PCV is gone.
The DV will need to be unbolted and removed for inspection. This is a little more involved but not beyond a home mechanic with a trolley jack and a decent socket set with torx fittings. Common problems are the rubber diaphragms in earlier revisions splitting resulting in a real lack of power from the engine. You can either replace with a new version (D or G) or go for an after market upgrade, like a GFB DV+ or Forge option.
These may not solve your problems but worth checking none the less! Good luck.
