Yikes. Im always afraid of clogging my cat. Those gaskets before the o2 sensor make a HUGE difference, I had no idea.

Also, if you're still having rough start issues, check the coolant temp sensor. One of the wires on mine just broke and I thought of this thread. Same symptoms. It will start if I crank it just right. But then as soon as you tap the gas it dies. If you stab at it just right while the rshared_pm is rising you can "break through" it and rev the car up...still misfires like crazy till its warm though. So I unplug the MAFs and the car fires up...haha.