I have a 87 vette with a 406 in it , it runs great , but on the interstate at 2400 rpm it starts to pop , breaks up ! If I disconnect the EST connector or unplug the ESC module , it doesnt do it ! I have replaced the ESC module , knock sensor , and the distributor ! Any ideas ? Any troubleshooting guides with those symptoms ? I know its in that circuit ! ..............Thanks !