Eating up O2 Sensors -- Running Rich

My car has been running rich for quite some time now. Replacing O2 sensor doesnt help (have to replace it once a year!). What is causing this thing to run so rich? Occasionally I throw the running too rich code but it will turn off.

Somehow, I passed smog today but 61/61 on Hydro Carbons (maxed!). I'm sure the problem is related. And if I get on it, there is a good amount of black smoke.

What is causing this? MAP? Still runs rich after full tune up too...