I read one post where you said you have a "regular" thermostat. I don't know what that means. You need a high flow thermostat. I recommend a 160 high flow. It you have a standard flow thermostat, you may as well throw the high volume water pump in the ditch, because the water still has to go through a standard flow thermostat. It's a literal choke point. The goal with a good cooling system is to get the coolant out of the engine as quickly as possible before it has a chance to heat up. Same theory with the 160 thermostat. If the coolant is allowed to get out of the engine at a lower temperature, it has that much less chance of over heating.
