2002 Pontiac Grand Prix Sluggish Engine

I have a 2002 Pontiac Grand Prix GT, 40th Anniv. Edition. I am having problems with the engine trying to stall, especially with the air conditioner running. The catalytic convertor was recently replaced due to the sulfur smell and also the air filter was replaced. The car also jerks when accelerating uphill. When idle, it sometimes almost dies (i.E. Sitting at a stop light). This car has 73,000 miles on it, has not been on any long trips, probably no more than 75 miles or so at one time and has never been wrecked. Any assistance will be greatly appreciated. Thank you.