My 2001 Pontiac Grand Prix won't pass smog!!?

[Jessica]

Can any one help me?! I have a 2001 Pontiac Grand Prix GT that just won't pass a smog check. I first took it to my company's mechanic and he ran a computer scan and a diagnostic check. It came back reading that the Mass Airflow sensor needed to be replaced and the EGR valve needed to be cleaned. I bought a brand new Air flow sensor and installed it myself and the mechanic cleaned the EGR valve. He had told me to reset the computer by disconnecting my battery for a while. I did that, the "check engine light" disappeared and the car runs great and saves me a lot of gas. They had told me to run it for at least 100 miles for the computer to register that the mass air flow sensor was fixed. I put about 140 miles on it before I took it to get smogged but it failed the test because it had high emissions reading! I asked the person that did my smog check what I could do about it and all he said was it'll cost me a couple hundred dollars and to ask a mechanic. The mechanic I first took it too said that all I needed was a tune up. The second mechanic did a diagnostic check and told me that if I already had a smog check that I shouldn't need one until the next 100,000 miles. I'm so confused can any body suggest what I could do so I can pass the smog and stop spending any more money??