Yes, that connector IS on and tight and is a pretty tight fitting one
but maybe it is worn?   The  AFM was recently replaced with a rebuilt
one too.

The fact that the issue has always gone away after the engine warms up,
eg warm up cycle, seems to point to coolant sensor or it's circuit I
believe.

-john

On 12/6/16 9:53 AM, Dan N wrote:
> /"stumble and run rich on accelerating at some point soon afterward"/
>
> this symptom is very similar to when I forgot to put the connector
> back on the AFM...
>
> could that connector be worn and not giving a tight connection?