I've been told it could be something to do with the converter, or else someone in the car is not telling the truth .

sulfur...that is what most often causes that smell...Somehow you're getting a wiff of sulfur dioxide...and i'd agree with the converter idea (assuming noone else is there lol). But then again, it could be something in the air and you just happend to drive through it.

I read that Carbon based in-cabin air filter addressed that problem.

Suuuuuuuuuuure you didn't fart. It will stain the leather! Cut back on the burritos!

It usually happens when you run the car hard, and the cats can't efficiently deal with the exhaust flow.

If it happens when you're just running easy and turn on the AC or heat, something else is wrong.

You could try switching to a different brand of gas to see if that helps.

I have noticed that as well, and it comes when I turn the AC off, but leave the fan running, it seems like it is pushing stale air through the vent for a few seconds or something. I thought it was the cabin filter, but still did it after changing. Not a huge deal, but I guess you could complain to the dealer about it :-)

Is the smell only in the car? Does it smell like that when you are in your house? Office? Do people stand away from you? Just a thought?

I have a 04 Toyota 4Runner Limited 4x4 and have had the same problem. It has been in for service already, fixed, and seems to be coming back after a few thosand miles, and a known problem for Toyota. I get a rotten egg smell when running the engine hard. The problem is the catalitic (sorry about the spelling) converter. This is not good since I am going to be ordering an 06 G35 coupe 6MT within the next month or so.

could be just a ECM program issue, back 02 sensor or cat is going.

The smell is sulfur dioxide, and it is coming from the catalytic converter in the exhaust system. Catalytic converters are on all modern day cars to clean the exhaust gas emissions to a passable level. That's why we have to burn unleadede gas. The converter creates the smell when the exhaust contains unburned hydrocarbons. As someone said earlier, this can occur after a hard run when the flow thru the converter is a bit more than it is designed to handle on a continuous basis.

If it smells like that all the time, then you may have a problem with your emission control system. However, I'd think it would set a code on the onboard computer. Any changes recently? Different brand of gas? How's the mileage now compared to earlier? A bad oxygen sensor could cause a problem, but again, I think it would set an engine diagnostic code. Does your state have a yearly mandatory vehicle inspection? Those places can tell you if your exhaust emissions are "legal" or not.

The smell that I described is not the cat for sure, and its not my @$$ either, it just happens instantly after I turn off the AC for about 2 minutes and then goes away. And if your catalytic converter is going byebye, you will most likely have a check engine light since the after cat O2 censor/s would complain.

Don't worry man, its OK to buy the car

Great explanation tennsmith

The smell is sulpher and you usually get it when you floor your car. It means a couple of things: Your car is brand new or you just had a new exhaust put it in. The smell wears out after time (a couple thousand miles, maybe?). If neither of these are the case, it means you have a bad cat.

Hope this helps.