carbs have been rebuilt,new vro pump, fuel system all redone, checked stator, coils charge coil. when the engine overheated a month ago the rpms dropped down to 2400, I believe this is the s.l.o.w. system working. Repaired overheating problem, now the engine won't run over 2400. iis there a blocking diode in the wiring and if so at what location, and can it be removed. If not how can I test the cd4 box. I hope someone can help here getting desperate 