I have a 1998 Blazer 4x4. Recently it started missing on the interstate and threw the SES light. Dealer put in new plugs and wires and it did the same thing. They then changed fuel filter and ran some injector cleaner. I have replaced the coil, ignition module and EGR valve. I have also cleaned the throttle body, MAF and IAC. Now it misses at idle, and at highway speeds. It is really bad while sitting in traffic. I ran some Seafoam through the vaccuum line and some through the gas but it didn't solve my problem. Could it possibly be the fuel pump going bad? Any suggestions are welcome at this point.