Bizzare problem

[RPM427]

This has been going on for a couple weeks now. Here are the symtoms: When the engine is cold (like sitting over night) then car will idle really low (300 rpm) and ussually die if I don't give it gas, sometimes it will just idle at 400 and then rev up to normal idle (900). When it is idling low the volt meter drops to about 6 - 7 volts.

When I am driving the car, it is down in power and runs rough. like a lawnmover. I borrowed a scanner from my uncle (he runs a Sunoco station) and hooked it up. A few problems came up after the testing cycle. First, EGR sensor contaminated, O2 sensor bank 1 short. I had cleaned out my EGR about 3 months ago when the gasket between the EGR plate failed. I cleared the codes and did it again. Only the o2 sensor came up. The fuel pressure was OK (about 38 psi at idle) . I checked the o2 sensors with this $5,000 graphing volt meter that I borrowed. the voltage was low idicating that the sensor thinks the engine is running lean. All the other sensors are saying the engine is running rich. It is def running rich becuase if I try to accelerate when the engine is cold, it makes small backfires, and at night you can see small flames coming out of the exhaust. Also, when the engine has been sitting overnight, if I try to accelerate, it makes these knocking/banging sounds, like someone hit the heasders with a mallet.

I changed both o2 sensors (I have that 3 day battle in a different post, funny) and the problem went away for a few days. but now it is back. If I disconnect the battery for a while then hokk it back up, the car runs like normal for about 10-15 minutes then suddenly goes back to the way it was.

I don't have access to that equipment until sat and I really need ideas. Anyone???