79, have you received any updates from Mastro? Did they do a compression test?
VW TDIs (in the current version) have problems with their High Pressure Fuel Pumps (HPFP) disintegrating. This requires more than simply replacing the faulty pump, because when this pump fails, it sends metal fragments throughout the fuel system (TDIs recirculate the fuel, so these metal fragments end up back in the fuel tank and everyplace else that fuel flows). The repair requires replacing the ENTIRE fuel system, to the tune of $8000!
At first, VW was blaming customers for accidentally putting gas into their tanks instead of diesel, or blaming the fuel supplier for mixing in gas or water that was causing these problems. As more and more customers were able to prove that none of these issues existed, VW started to back down. To further back VW into a corner, many TDI customers filed NHTSA reports, so now the NHTSA is investigating the TDI HPFP issue. I'm sure VW is not comfortable with this, and so now has started paying for this $8k job even for customers with HPFPs that fail outside of warranty.
I'm simply sharing this story so that Impreza owners can consider filing NHTSA reports regarding oil consumption. This will be most compelling if the situation could be considered dangerous and not just inconvenient (for example, "My oil light came on while I was driving on a 6-lane highway, and I panicked because I knew that I had to shut off the engine ASAP, but was having trouble getting to the shoulder of the road, which also would have been dangerous on such a busy highway").