I have a 1993 chevy silverado with a 5.7 , the truck has 135000 miles on it, but started running terrible, rough idle, hesitation, misses, won't get out of its own way, I read the codes, called for egr valve and map sensor, I replaced with new, also egr solenoid and fuel filter, new cap, rotor wires and plugs, after all that, the code still read egr, I'm losing my mind and don't know what else to do, there's plenty of vacuum from the tbi but something is still messed up....PLEASE HELP