i have been having trouble with my blazer i bought a few months ago. It cuts out and sputters alot but sometimes it runs fine. I did a full tune-up and changed the fuel filter fuel pump. This made no difference, so i took it to a local shop that has made a good name for it self. the guy told me my truck has a computer in it and if something is wrong with it there is no way to fix it. Is this really true? What does this computer do and can i get a new one?