A dirty maf will certainly cause the trans to slip and I have witnessed that first hand, OR if you have made a recent change to your intake plumbing/air filter. A larger pipe/filter/throttle body means slower airflow across the sensor and if it reaches out of range far enough it will cause the trans to be low on pressure. It will also cause the car to run too lean at WOT and all normal driving which means your fuel trims will be reading positve quite a bit at the same given time. Regardless, if the maf sensor is dirty the problem will exist all the time, not just once in a while. This was also a problem when using an AFC when it came out. You could make adjustments soo far and then it would cause the trans to slip if making big changes to make the number read lower. Also if the maf table in the pcm was tuned far from stock it can cause low trans pressure. Your problem really doesnt connect with a dirty maf sensor but you could always check your fuel trims and then clean the sensor and see if anything changes.
