I suspect either a faulty temp sensor or a bad ground in a temp sensor circuit. The grounds all come together (a bunch of thin white wires) to a mounting screw on the manifold. This includes grounds for sensors and injectors. Clean them all and apply a little anti oxidant paste. The coolant temp sensor is the more important of the two and is mounted in the side of the block. Resistance in both of these sensors declines as the car warms up yet you say that readings indicate higher resistance when warm. If that is actually happening, the ECU is reading that the engine is getting colder rather than warmer and could be calling for such long injections that the engine is flooding. Is there some way for you to measure unbured hydrocarbons coming out the tail pipe. If excessive when engine is warm, may be the temp sensor is it.