Originally Posted by EagleMark
You can't set timing by ear.... these CCC and all GM EFI systems are usually set to 0 advance with Bypass wire disconnected, usually a tan wire with plug from the EST-ICM modle in distributor. ESC is module for knock system retard, Disconnect this wire and set timing to 0 with light. Then when plugged back in ECM will control timing and can be 10 to 20 degrees advanced. Will also set a DTC so disconnect battery to clear codes.
Cool, that clears things up a bit.