Hi all.
Have just started encountering a problem with my 11' SD4 HSE. When selecting Drive or Reverse the Revs will dip to 600 then go back up to 800.

It feels like its going to stall, especially when pulling up to a junction etc, it hasn't yet!

I'll attach a video showing the problem.

I've tried to do a bit of digging but no concrete answer. Software, throttle body, ATF?? Any ideas?

https://streamable.com/jhzxdj

Thanks