Andrew-


OP says it runs OK on cold start, but then when it warms up it runs poorly.... when cold the DME ignores AF readings from the (cold) O2 sensors, and instead runs a 'rich' map.... then, when it comes up to temp, it then uses the o2 sensors.


If the car has an air intake leak, this 'cold start rich period' would be fine...then when the DME uses the O2s, he is now lean. (becuase air is getting in that the DME doesnt know about...)


OP, dont look at CATs yet, lots of stuff can fool the DME into thinking cats are bad