[A26B]

Re: Slowing down the stock Pump or adding an electric pump.

Reducing the coolant flow rate to impede or retard the bypass valve opening is not going to do anything to provide the additional cooling needed to compensate for the additional heat generated by running the engine at higher power levels.

The cooling limitation is the capacity of the heat exchanger/radiator. What is needed is more capacity, not less water pump volume. There's a lot more to cooling the LT5 than what goes on outside. The flow rate needs to be high enough to "scour" steam bubbles from hot spots.

Big pulleys & electric pumps are fine for more horsepower, removing parasitic engine drag, but they don't yield more cooling capacity.