I wouldn't get get too excited about idle AFR if your cam has any serious overlap.

Make it idle happy and let the AFR land where it lands.

My stone age 950 Commander TBI wouldn't idle consistently closed loop with an MP509. It would idles nice and clean and the next time you started it, it would barely run. We had to run it A/N to 1800 and have it switch to make it behave. Apples to oranges maybe compared to the new stuff but it just could not deal with low speed reversion.

I think this might be slightly less of an issue with port injection.

Kevin