Smell of sulfur/dies when slowing down

The smell is caused by un-burnt fuel going through your catalytic converter or possibly you have a bad catalytic converter...which is warrantied for 80,000 miles. If it is just un-burnt fuel then you probably have a misfire in one or more of your cylinders which explains the loss of power. Check the spark coming from the coils...don't get shocked!!! If one of the coils is not giving good spark then swap that coil with one that is giving good spark. If the problem follows the coil then replace the coil. If the problem stays in the same place then replace the ICM. If all coils test out good then check the air restriction valve to make sure it is working properly, installed properly, and aligned properly. Also replace plugs/wires if they have not been done in 40,000. If none of those then get a high flow catalytic converter from summit racing and have a muffler shop switch it out. Here is a link to a forum where you could get further help...and the thread it is linked to deals with your particular problem.

http://www.pontiacbonnevilleclub.com/for...

You do not need a new car, just need to figure out why it is not firing on all cylinders!