99 ML320 Not Shifting Right
 

Hi All, I have a 99 ML320 that is not shifting properly. While driving lets say 20miles per hour and I floor it, the RPM revs up (5000 RPM) yet the car bogs down and keeps on driving at 20miles an hour. Once I release the gas paddle I feel and hear a thug sound from the trany. Has anybody ran into this issue.

Quick background: 1- The Air Mass sensor was replaced not too long ago due to check engine light.
2- The gas paddle assembly was replaced by the dealer because they thought it was causing the shifting issue. (well it came back).
3- the fuel injectors were cleaned as part of the troubleshooting steps (To no help).

The trans is computer controlled, have codes read to diagnose.

Well it is at the dealer today. They are suspecting the Mass Air Flow sensor as being deffective. I am in a wait and see mode now. The dealer kept it overnight.