EXPERT ADVICE NEEDED

2004 A6 2.7T SLINE - I got this cream puff in 2012 w/89k miles from the original owner who had all service, including the 90k stuff done at the dealer. I work from home so don't drive everyday. In 2014, I was relocating to Henderson, NV and she popped up 0172/0175. I was leaving the next day and my local guy said no problems, probably O2 Sensors and get them replaced after the cross country drive. Drive was fine, except for the typical rough idle and less than stellar gas mileage. Upon pulling into the parking lot of the hotel we were staying at until the moving truck arrived, the rear water pump went. After some research, I had the car towed to a place for repair, of which they also replaced the front O2 Sensors. Mileage is 108168 after work was complete, got the car inspected and all was Ok. 1500 miles later, P0172/0175 displayed. Put some octane booster in and performed a reset. Also replace the Air Filter. 100 miles later, P0172/0175. I cleaned the MAF and got 400 miles, and then P0172/0175. I replaced the MAF. Another 200 miles, P0172/0175. Took it to a local shop who charged a healthy diagnosis fee and complete vacuum leak testing, they concluded, replaced Air Intake Hose Throttle body, breather hose, purge valve and booster check valve. 500 miles later P0172/0175 again. If I perform a reset, it is like a magic button and the engine purrs like a kitten. I am afraid I am simply paying for OJT on my dime. Any Suggestions are appreciated. I also can tell that I have some type of very minor oil seepage because after the car is parked for a few days, I will fire up and the first 5 minutes, I can smell oil burn, but then it is gone after burning off. Other than this issue, the car is perfecto. Thanks in advance, Eric.