At 65k, I had a transmission torque converter failure. Symptoms were shuddering / surging during particular types of acceleration. At first the dealership "could not reproduce" the shuddering symptoms. Within days, a warranty repair necessitated by a complete transmission failure. Now at 81k miles, the symptoms have returned. The dealership diagnoses a "mass air flow sensor" failure that is not covered by my 100k power train warranty. How can I be sure I'm not again dealing with a torque converter failure? What can I do to force the dealership to confirm their diagnosis? My power train warranty time expires in 1 month.