Did this permanently fix your problem? I have had the exact same symptoms - and when I replace the 02 units, the problems mostly go away (though it still misses a little tiny bit at idle. Then, after about 3 or 4 weeks, then the new O2(s) go bad!!!

I checked for vacuum leaks - there are none.

I replaced the MAP sensor - didn't help.

New plugs, wires, cap and rotor - didn't help.

Clearly, something is making the car run rich and miss, until the O2 sensor(s) get crudded up with carbon - then they fail and I get the P0171 code.

 

When you gun it while you're driving, do you hear a whistling or whining noise? You might have to listen for it.

If you do, check your manifolds. It's not uncommon for the bolts to loosen up and let a small amount of air in.

 

I had identical problems - rpms dipping to 500 when coming to a stop and then bouncing right back to nominal, chugging at 2000 rpm and bad fuel economy. Also had the P0171 System Too Lean code. Replaced the upstream O2 and so far so good.