Change the MAF
(by way of explanation, the MAF can appear to be working fine but actually be operating at the extremes of plausible values. It doesn't throw a code because it is giving values, and the ECU can compensate with the feedback from the O2 sensors, but the MAF is critical for the ECU to feed the TCU engine load information. If its at the limit of plausible it can confuse the TCU leading to erratic shifting. Its also considerably cheaper to change the MAF as a first step than to pull the transmission out!)