about a month ago my blazer one morning started 2 missfire only a couple hundered rpms before it would shift gears. it happens in any gear and at any rpm and weather its hot or cold and it comes and goes. it happened about an mouth after i installed a new computer cause the other one fried. i have cleaned my ait fiter changed the fuel fiter replace the fuel pump(went bad before this happened), installed new sparkpulgs and cap and rotor, and plugs, i did all this about a month before this started happening. i can not figure out y this is happening and no code is being throw other than one that stays on cause my new computer apparently came froma califoria truck and the computer cant be reprogammed because of the emmissions set on the computer. does any one have any suggestons on y this is happening?