Audiboy

but chances are it's an ignition problem. It sounds like you have one or more bad plug wires. That, or maybe the plugs are bad. If those look good, then even moisture or water on one of the coils can cause such misfire. Hopefully it's not one of the coils themselves

If it's not the ignition, then it's the MAF. I doubt it's the MAF because with a bad MAF, it should idle fine, but when you give it gas, it will stumble. You can check this out by disconnecting it, resetting the ECU and driving the car with a disconnected MAF. If it runs fine (don't drive it too hard), then the MAF is bad. Note, no MAF connected is not equal to bad MAF. Bad MAF will keep the ECU voltage sensing stuck at lean. If you floor it, you can overcome the MAF with the programmed WOT readings, and the car will accelerate briskly again. If there is ignition problems, accelerating all the way to WOT will make things worst since denser air/fuel needs more energy to ignite. So that's how you can check next time.

And what you smell from the cats is not due to a plug cat. It's because it is misfiring and there is raw gas going through the cats.

A plugged cat will not show symptoms of stumbling as you described. Just a choked response - like pulling a heavy trailer going up a 30% incline on 5th gear at 2000 rpm - you get my drift

Hope they fix it, but doesn't sound like something serious (ie engine)