The exhaust smell of my car smells as if it is of unburnt fuel. What can be the problem?

I went for tune up just 1 week ago. Mechanic adjusted tappets and cleaned throtle but I am not satisfied by tappet adjustment because while coming back to home after tappet adjustment, my car was overheated.I went back to his workshop. He just changed temperature sensor and said every thing is fine now. Also fuel consumption has little bit increased from that day.

As far as the exhaust is concerned, I changed a gaskit that was of exhaust system about 2 months ago but I think there is a problem with it also because I can feel the heat of exhaust gasses when I place my hand over the area from which exhaust pipe originates.