I had my 96 Mongte Carlo LS at my mechanics the other day because it was idleing very royugh and felt like it was having some trouble going. He ran a code diagnostic on it and told me I was getting a multi cylinder misfiring code. He told me to change the plugs and wires and that should do the trick. So I changed my spark plugs and wires and nothing changed, still misfiring. So next came the coil packs. Still nothing. Also about a month ago I changed the fuel pump/filter and fuel pressure regulator. I love this car but I am beggining to fear the worst :-/ does anyone have an idea what could be cauing this? Does the EGR valve or mass airflow sensor cause this problem too? Thanks!