I drive an 2005 Automatic 350z. A few days ago, i really pushed the car accelerating rather quickly. When i came up to the red light and began to stop, the car stalled out. I edged over to the side of the road, threw it in neutral, and turned the key and it started right back up. A few miles down the road i was at a red light and the rpm's dropped very low and the engine started shuddering. After a few seconds, it revved back up. It did this 3 times while waiting at the light. (This is the first time i have had the stall issue but the second time i have had the shuddering engine issue.) I went to Autozone and they ran the codes and it came back with nothing. Now they and a few other people have given me "ideas" of what it could be with no guarantee or no test to check for it. Some of the possible ideas were: bad alternator, bad vacuum, bad TPS, dirty or faulty fuel pump, rusted out catalytic converters, blown out spark plug, and bad battery. The battery was checked and shows that it is good. I doubt it is the alternator cause my voltage is staying consistent. Anybody have any idea of what it probably is?

Sidenote: the vehicle was originally from Florida and the Catalytic Converters are pretty rusted on the outside. Planning on replacing the whole exhaust with a Concept Z Performance system within the month.

I've fixed your thread title. Just a friendly word of advice, try using a more descriptive title. The average person will just ignore titles that are simply titled "Please help". You're trying to get knowledgeable people to look at your thread, so putting the issue in the title will attract attention.

Have you had your electrical system checked? I'd start there first. When was the last time the vehicle was in for service? Sounds like it may be due.

If the car was a Florida car, it may have been subject to salt air corrosion. A good place to start is checking the several ground wires attached to the engine block.

I'd start by cleaning the Tb and doing a TB relearn. Idel air is managed by the electronic TPS so a dirty or sticking TB could be causing the issue, as could a bad TPS.

Have you cleaned or replaced your air filter lately?
You could also have something interfering with the MAF sensor. The only reason I mention it is I had this happen couple of years ago in the fall with a tiny leafy bit about the size of a grain of rice.