Mazda 6 Service Manual: No.20 noise occurs at idle when vehicle is stopped in all positions/ranges

No.19 excessive shift shock on torque converter clutch (tcc)

No.21 noise occurs at idle when vehicle is stopped in d, s, l ranges, or in r position

Other materials:

Mazda 6 Service Manual: Instrument cluster removal/installation
Caution When replacing the instrument cluster, the configuration procedure must be performed before removing the instrument cluster. If the configuration procedure is not performed before removing the instrument cluster, it is possible that the instrument cluster will not operate normally. ...

Mazda 6 Service Manual: Driving on Uneven Road
Your vehicle's suspension and underbody can be damaged if driven on rough/uneven roads or over speed bumps at excessive speeds. Use care and reduce speed when traveling on rough/uneven roads or over speed bumps. Use care not to damage the vehicle's underbody, bumpers or muffler(s) when driving ...