My car passed SMOG despite the potential of P0171 at idle:
Test 2021-Final → 2021 (prior 2 tests)
15mph 81 → 357-> 578 (from highest 578 to 81)
25mph 44 → 1079-> 639 (from highest 1079 to 44)
This is a 1999 with 144k miles. Emission levels are amazing! These are better than what I had 10yrs ago.
I still have to figure the Fuel Trim maxing out on idle! I was going to change the IAC but saw some improvement (unsure its lasting improvement) so instead went for the SMOG. I will be pursuing a diagnosis.