What Can Cause White Smoke From an Exhaust System After Changing The Head Gaskets and Catalytic Converter and only last a few seconds and doesn’t do it again? I have a 2000 Pontiac Sunfire SE Sedan! I have a Pacesetter Monza Exhaust System, AEM Cold Air Intake, and a MagnaFlow Hi-Flow Catalytic Converter. When I had the New Hi-Flow Converter put on my car, I had the head gaskets replaced with brand new ones. I also had the oil changed at the same time since it needed it soon anyways. So recap, new gaskets, converter and oil (check). When I first started my car up after I got into it, I let it idle for a little bit to warm up before I took off. The car started to smell like something burning. Then I put the car in reverse and POOF, comes out a white cloud of smoke that only lasts a few seconds! The car ran a few marks above 195 for that day sometimes rise a few more than that. but since running the car a month since that happened, it doesnt smoke, smell, or run extremely hot. before I had this all done, the car would heat up quickly when idleing. going up in temp 6-7 marks above 195. since then it only idels 2-3 marks above 195. still a problem with overheating. Im clueless on what is the problem. new converter, gaskets and a oil change and still overheating problems. I also had the Spark plugs changed and the wires. With all the new parts, I have noticed the car idles @ or around 500-1000rpms which I think is pretty low since it should run around 1000-1500rpms right? a trained Mechanics Help would be appreciated. I want serious answers only, no uncalled for answers!!! Thanks for any help and hope this helps in diagnoseing the problem!