It has a 350 Rocket in it, with a 4 week old Eledebrock Carb, and intake. During the 4 week period of having it on. It Ran like a champ, but now for some reason. It runs good for 15-20 minutes, but after it reach normal operating temperature,. It starts running like a tired dog. Only goes 10-15mphs, What could cause something like that? Bad Coil in the distrubutor? New spark plugs and wires, Rotor Button and cap 2 months old.