I have done some more careful observation and I have narrowed it down;
I start car with foot on brake.
I turn key.
Car revs to about 1200 rpm. Keeps revving, with or without my foot on the accelerator.
I reverse, back out, it dips to about 1000 rpm.
Put it in drive, it drops to 800 rpm.
Maybe this is just normal and
I am being too picky? It didn't do this during the first month of ownership, though.
Is it just a PDK thing? Issue is high revs at start up.
And sadly, no PSE.