I built a 350 with fairly aggressive cam edelbrock intake and standard heads for my boat. When it gets to operating temp it refuses to rev past idle. Sits and makes a chugging sound. When it does this the tach drops very low and the voltmeter is all over. When the engine is cold no problems runs like a champ.i tried replacing the coil thinking it was getting and shorting out no change. Tried slowly adding fuel into the carb when its doing this thinking if its a fuel issue adding fuel would bring it out of it. If i leave it with throttle but refusing to rev it will backfire hard and shut off. Restarts immediately.