2001 Hyundai XG300

My cars acts like it wants to cut off, the tacometer is going up and down on several occasions, with a kind of jerking motion. Then it goes back to the speed. I mentioned this to the mechanic on sevral occasions, however it did not do it with him driving, until finally I had him to change SPW and the SWPlugs, along with the fuel filter, air filter. The car now has the engine light on, (Friday) and acted like it wanted to shut off again only worse this time while driving, and I felt that I was not going to be able to make it to my home. I have not driven the car since Friday 5/23/09
PS. I also had the Mass air flow sensor changed less than a year agoand recent oil change, tires and etc.