2003 passat wagon

I have a wagon GLS and I have been having one problem after another. 2 months ago it was the altenator, this month is was the therm. as well as the mass air sensor. I have been taking it to a very good service center that specializes in VW. The car only has about 65k on it. 2 days ago it was ideling rough and that is when we put found out about the mass air sensor, so after it was replaces it idled great but didn't have enough power to pull itself up the drive. We unplugged the o2 sensor which should have tripped the check engine light (but didn't) but now the car runs great (for now)
any suggestions as to what is causing all these problems. I understand the alt problem, the car idles alot with the a/c on so I am cool with that but the o2 thing and the mass air.
I need some help

All cars manufactured today contain at least one computer. It is in charge of monitoring engine emissions and adjusting the engine to keep emissions as low as possible. The computer receives information from a many different sensors, including:
• The oxygen sensor
• The air pressure sensor
• The air temperature sensor
• The engine temperature sensor
• The throttle position sensor
• The knock sensor
• The oxygen sensor
Using the information from these sensors, the computer can control things like the fuel injectors, spark plugs and the idle speed to get the best performance possible from the engine while keeping emissions low. The computer can also sense when something has gone wrong and can inform the driver with the "Check Engine" light. A mechanic can read a diagnostic code from the computer and fix the problem. Nowadays Volkswagen to release next generation Passat in 2011 with high quality sensor to easily determine the problem your car.