What is the chemical make up of the stuff that comes out of the car's exhaust pipe? Is it CO or CO2 or someth

It's actually quite a few gases: CO2 is the major one, a product of complete combustion of fuel (causes the greenhouse effect), CO (if there's inccomplete combustion, but it is mostly taken care of by the catalyst) and the second major product is water. Depending on fuel quality it could also be NOx (mixed nitrogen oxides, which cause smog and can produce ozone by reacting with oxygen in the air), SOx (sulfur oxides, mostly from the old diesel motors, although new laws should reduce it significantly), and also unburned hydrocarbons, the constituents of fuel.