904 vs 999

As to #1;
I'm gonna go out on a limb here and say, the engine has too much Idle Power is why it bangs. Take some Idle-Timing away, and see what happens. It could other but this is the easiest test.

As to #2
the trans should NOT be going into LU that early, the RPM is way too low. Has the rear gear ratio been changed or really tall tires installed, cuz either of those are gonna affect the governor.
As will the KD adjustment and the line-pressure. I would be hesitant to blame the one specific model or year for these annoying characteristics.
  1. Initial timing is 2* BTC, so I will say I don't think it has too much timing.
  2. Almost all of these types of 3-speed lock ups I've owned have always locked up in 3rd gear around 45 mph. I don't know what anyone else has experienced, maybe they will chime in.