PO172 on a 98 Prelude SH

My systems running rich, so says the computer. In observing the o2 sensor I
found that voltage does indeed spike just as the engine returns to idle. At
this point it hesitates and stumbles, barely running for a few seconds.
After that, idle returns normally and sensor voltage occilates between .2
& .8v like it should. Long term fuel trim is -%20%, short term -4% or so.
I checked the map sensor and it is reading about 1.5 inHg off from my
vacuum gauge, but I wouldn't think this small discrepency accounts for the
condition.
I haven't checked fuel pressure or the dampner yet, I'll do that
tomorrow. I was just wondering if you brains with a lot of Honda
experience have run into something like this before. Thanks.