you may want to check your 3800 fuel pressure regulator
for a leak through the diaphragm. Cold, your engine needs more fuel. Warm, your car doesn't need as much fuel and too much fuel will flood cylinders. (Rotten egg smell means your catalytic converter is working. It also would mean your are running rich. not a sign of converter being bad)
you will need to watch the misfire counter to see what cylinders are misfiring when your car is running bad. Is it always certain ones or is it random, or all of them. Is it tied to certain cylinders that are tied together at the coil packs? Spark plug
wires could be shorting too. See what the fuel trims are when the car is acting up. There are so many thing that can interrupt normal performance. Watching what your computer sees and how it is reacting is one of the best things you can do to diagnose what is happening.